Self-denial is the first and great lesson in the School of Jesus Christ

"Then Jesus said to his disciples, “Whoever wishes to come after me must deny himself,* take up his cross, and follow me." (Matthew 16: 24)

In the scripture above, Jesus Christ laid down the core principle of discipleship.  The lesson is called the first and great lesson in the school of Christ.  I have little to offer on this.  Instead, I will offer two great commentaries from John Gills Exposition and Matthew Henry Commentary:

John Gills Exposition:
"Then said Jesus unto his disciples
Knowing that they had all imbibed the same notion of a temporal kingdom, and were in expectation of worldly riches, honour, and pleasure; he took this opportunity of preaching the doctrine of the cross to them, and of letting them know, that they must prepare for persecutions, sufferings, and death; which they must expect to endure, as well as he, if they would be his disciples:

if any man will come after me:
that is, be a disciple and follower of him, it being usual for the master to go before, and the disciple to follow after him: now let it be who it will, rich or poor, learned or unlearned, young or old, male or female, that have any inclination and desire, or have took up a resolution in the strength of grace, to be a disciple of Christ,

let him deny himself:
let him deny sinful self, ungodliness, and worldly lusts; and part with them, and his former sinful companions, which were as a part of himself: let him deny righteous self, and renounce all his own works of righteousness, in the business of justification and salvation; let him deny himself the pleasures and profits of this world, when in competition with Christ; let him drop and banish all his notions and expectations of an earthly kingdom, and worldly grandeur, and think of nothing but reproach, persecution, and death, for the sake of his Lord and Master: and

take up his cross;
cheerfully receive, and patiently bear, every affliction and evil, however shameful and painful it may be, which is appointed for him, and he is called unto; which is his peculiar cross, as every Christian has his own; to which he should quietly submit, and carry, with an entire resignation to the will of God, in imitation of his Lord:

and follow me;
in the exercise of grace, as humility, zeal, patience, and self-denial; and in the discharge of every duty, moral, or evangelical; and through sufferings and death, to his kingdom and glory. The allusion is, to Christ's bearing his own cross, and Simeon's carrying it after him, which afterwards came to pass."  (John Gills Exposition)

Matthew Henry Commentary:
"
Verses 24-28 Christ, having shown his disciples that he must suffer, and that he was ready and willing to suffer, here shows them that they must suffer too, and must be ready and willing. It is a weighty discourse that we have in these verses.I. Here is the law of discipleship laid down, and the terms fixed, upon which we may have the honour and benefit of it, v. 24. He said this to his disciples, not only that they might instruct others concerning it, but that by this rule they might examine their own security. Observe,1. What it is to be a disciple of Christ; it is to come after him. When Christ called his disciples, this was the word of command, Follow me. A true disciple of Christ is one that doth follow him in duty, and shall follow him to glory. He is one that comes after Christ, not one that prescribes to him, as Peter now undertook to do, forgetting his place. A disciple of Christ comes after him, as the sheep after the shepherd, the servant after his master, the soldiers after their captain; he is one that aims at the same end that Christ aimed at, the glory of God, and the glory of heaven: and one that walks in the same way that he walked in, is led by his Spirit, treads in his steps, submits to his conduct, and follows the Lamb, whithersoever he goes, Rev. 14:4 .2. What are the great things required of those that will be Christ’s disciples; If any man will come, ei tis thelei —If any man be willing to come. It denotes a deliberate choice, and cheerfulness and resolution in that choice. Many are disciples more by chance or the will of others than by any act of their own will; but Christ will have his people volunteers, Ps. 110:3 . It is as if Christ had said, "If any of the people that are not my disciples, be steadfastly minded to come to me, and if you that are, be in like manner minded to adhere to me, it is upon these terms, these and no other; you must follow me in sufferings as well as in other things, and therefore when you sit down to count the cost, reckon upon it.’’Now what are these terms?(1.) Let him deny himself. Peter had advised Christ to spare himself, and would be ready, in the like case, to take the advice; but Christ tells them all, they must be so far from sparing themselves, that they must deny themselves. Herein they must come after Christ, for his birth, and life, and death, were all a continued act of self-denial, a self-emptying, Phil. 2:7, Phil. 2:8 . If self-denial be a hard lesson, and against the grain to flesh and blood, it is no more than what our Master learned and practised before us and for us, both for our redemption and for our instruction; and the servant is not above his lord. Note, All the disciples and followers of Jesus Christ must deny themselves. It is the fundamental law of admission into Christ’s school, and the first and great lesson to be learned in this school, to deny ourselves; it is both the strait gate, and the narrow way; it is necessary in order to our learning all the other good lessons that are there taught. We must deny ourselves absolutely, we must not admire our own shadow, nor gratify our own humour; we must not lean to our own understanding, nor seek our own things, nor be our own end. We must deny ourselves comparatively; we must deny ourselves for Christ, and his will and glory, and the service of his interest in the world; we must deny ourselves for our brethren, and for their good; and we must deny ourselves for ourselves, deny the appetites of the body for the benefit of the soul.(2.) Let him take up his cross. The cross is here put for all sufferings, as men or Christians; providential afflictions, persecutions for righteousness’ sake, every trouble that befals us, either for doing well or for not doing ill. The troubles of Christians are fitly called crosses, in allusion to the death of the cross, which Christ was obedient to; and it should reconcile us to troubles, and take off the terror of them, that they are what we bear in common with Christ, and such as he hath borne before us. Note, [1.] Every disciple of Christ hath his cross, and must count upon it; as each hath his special duty to be done, so each hath his special trouble to be borne, and every one feels most from his own burthen. Crosses are the common lot of God’s children, but of this common lot of God’s children, but of this common lot each hath his particular share. That is our cross which Infinite Wisdom has appointed for us, and a Sovereign Providence has laid on us, as fittest for us. It is good for us to call the cross we are under our own, and entertain it accordingly. We are apt to think we could bear such a one’s cross better than our own; but that is best which is, and we ought to make the best of it. [2.] Every disciple of Christ must take up that which the wise God hath made his cross. It is an allusion to the Roman custom of compelling those that were condemned to be crucified, to carry their cross: when Simon carried Christ’s cross after him, this phrase was illustrated. First, It is supposed that the cross lies in our way, and is prepared for us. We must not make crosses to ourselves, but must accommodate ourselves to those which God has made for us. Our rule is, not to go a step out of the way of duty, either to meet a cross, or to miss one. We must not by our rashness and indiscretion pull crosses down upon our own heads, but must take them up when they are laid in our way. We must so manage an affliction, that it may not be a stumbling-block or hindrance to us in any service we have to do for God. We must take it up out of our way, by getting over the offence of the cross; None of these things move me; and we must then go on with it in our way, though it lie heavy. Secondly, That which we have to do, is, not only to bear the cross (that a stock, or a stone, or a stick may do), not only to be silent under it, but we must take up the cross, must improve it to some good advantage. We should not say, "This is an evil, and I must bear it, because I cannot help it;’’ but, "This is an evil, and I will bear it, because it shall work for my good.’’ When we rejoice in our afflictions, and glory in them, then we take up the cross. This fitly follows upon denying ourselves; for he that will not deny himself the pleasures of sin, and the advantages of this world for Christ, when it comes to the push, will never have the heart to take up his cross. "He that cannot take up the resolution to live a saint, has a demonstration within himself, that he is never likely to die a martyr;’’ so Archbishop Tillotson.(3.) Let him follow me, in this particular of taking up the cross. Suffering saints must look unto Jesus, and take from him both direction and encouragement in suffering. Do we bear the cross? We therein follow Christ, who bears it before us, bears it for us, and so bears it from us. He bore the heavy end of the cross, the end that had the curse upon it, that was a heavy end, and so made the other light and easy for us. Or, we may take it in general, we must follow Christ in all instances of holiness and obedience. Note, The disciples of Christ must study to imitate their Master, and conform themselves in every thing to his example, and continue in well-doing, whatever crosses lie in their way. To do well and to suffer ill, is to follow Christ. If any man will come after me, let him follow me; that seems to be idem per idem—the same thing over again. What is the difference? Surely it is this, "If any man will come after me, in profession, and so have the name and credit of a disciple, let him follow me in truth, and so do the work and duty of a disciple.’’ Or thus, "If any man will set out after me, in good beginnings, let him continue to follow me with all perseverance.’’ That is following the Lord fully, as Caleb did. Those that come after Christ, must follow after him.II. Here are arguments to persuade us to submit to these laws, and come up to these terms. Self-denial, and patient suffering, are hard lessons, which will never be learned if we consult with flesh and blood; let us therefore consult with our Lord Jesus, and see what advice he gives us; and here he gives us,1. Some considerations proper to engage us to these duties of self-denial and suffering for Christ. Consider,(1.) The weight of that eternity which depends upon our present choice (v. 25); Whosoever will save his life, by denying Christ, shall lose it: and whosoever is content to lose his life, for owning Christ, shall find it. Here are life and death, good and evil, the blessing and the curse, set before us. Observe,[1.] The misery that attends the most plausible apostasy. Whosoever will save his life in this world, if it be by sin, he shall lose it in another; he that forsakes Christ, to preserve a temporal life and avoid a temporal death, will certainly come short of eternal life, and will be hurt of the second death, and eternally held by it. There cannot be a fairer pretence for apostasy and iniquity than saving the life by it, so cogent is the law of self-preservation; and yet even that is folly, for it will prove in the end self-destruction; the life saved is but for a moment, the death shunned is but as a sleep; but the life lost is everlasting, and the death run upon is the depth and complement of all misery, and an endless separation from all good. Now, let any rational man consider of it, take advice and speak his mind, whether there is any thing got, at long run, by apostasy, though a man save his estate, preferment, or life, by it.[2.] The advantage that attends the most perilous and expensive constancy; Whosoever will lose his life for Christ’s sake in this world, shall find it in a better, infinitely to his advantage. Note, First, Many a life is lost, for Christ’s sake, in doing his work, by labouring fervently for his name; in suffering work, by choosing rather to die than to deny him or his truths and ways. Christ’s holy religion is handed down to us, sealed with the blood of thousands, that have not known their own souls, but have despised their lives (as Job speaks in another case), though very valuable ones, when they have stood in competition with their duty and the testimony of Jesus, Rev. 20:4 . Secondly, Though many have been losers for Christ, even of life itself, yet never any one was, or will be, a loser by him in the end. The loss of other comforts, for Christ, may possibly be made up in this world (Mk. 10:30 ); the loss of life cannot, but it shall be made up in the other world, in an eternal life; the believing prospect of which hath been the great support of suffering saints in all ages. An assurance of the life they should find, in lieu of the life they hazarded, hath enabled them to triumph over death in all its terrors; to go smiling to a scaffold, and stand singing at a stake, and to call the utmost instances of their enemies’ rage but a light affliction. [3.] The worth of the soul which lies at stake, and the worthlessness of the world in comparison of it (v. 26). What is a man profited, if he gain the whole world and lose his own soul? ten psychen autou ; the same word which is translated his life (v. 25), for the soul is the life, Gen. 2:7 . This alludes to that common principle, that, whatever a man gets, if he lose his life, it will do him no good, he cannot enjoy his gains. But it looks higher, and speaks of the soul as immortal, and a loss of it beyond death, which cannot be compensated by the gain of the whole world. Note, First, Every man has a soul of his own. The soul is the spiritual and immortal part of man, which thinks and reasons, has a power of reflection and prospect, which actuates the body now, and will shortly act in a separation from the body. Our souls are our own not in respect of dominion and property (for we are not our own, All souls are mine, saith God), but in respect of nearness and concern; our souls are our own, for they are ourselves. Secondly, It is possible for the soul to be lost, and there is danger of it. The soul is lost when it is eternally separated from all the good to all the evil that a soul is capable of; when it dies as far as a soul can die; when it is separated from the favour of God, and sunk under his wrath and curse. A man is never undone till he is in hell. Thirdly, If the soul be lost, it is of the sinner’s own losing. The man loses his own soul, for he does that which is certainly destroying to it, and neglects that which alone would be saving, Hos. 13:9 . The sinner dies because he will die; hes blood is on his own head. Fourthly, One soul is worth more than all the world; our own souls are of greater value to us than all the wealth, honour, and pleasures of this present time, if we had them. Here is the whole world set in the scale against one soul, and Tekel written upon it; it is weighed in the balance, and found too light to weigh it down. This is Christ’s judgment upon the matter, and he is a competent Judge; he had reason to know the price of souls, for he redeemed them; nor would he under-rate the world, for he made it. Fifthly, The winning of the world is often the losing of the soul. Many a one has ruined his eternal interest by his preposterous and inordinate care to secure and advance his temporal ones. It is the love of the world, and the eager pursuit of it, that drowns men in destruction and perdition. Sixthly, The loss of the soul is so great a loss, that the gain of the whole world will not countervail it, or make it up. He that loses his soul, though it be to gain the world, makes a very bad bargain for himself, and will sit down at last an unspeakable loser. When he comes to balance the account, and to compare profit and loss, he will find that, instead of the advantage he promised himself, he is ruined to all intents and purposes, is irreparably broken.What shall a man give in exchange for his soul? Note, If once the soul be lost, it is lost for ever. There is no antallagma —counter-price, that can be paid, or will be accepted. It is a loss that can never be repaired, never be retrieved. If, after that great price which Christ laid down to redeem our souls, and to restore us to the possession of them, they be so neglected for the world, that they come to be lost, that new mortgage will never be taken off; there remains no more sacrifice for sins, nor price for souls, but the equity of redemption is eternally precluded. Therefore it is good to be wise in time, and do well for ourselves.2. Here are some considerations proper to encourage us in self-denial and suffering for Christ.(1.) The assurance we have of Christ’s glory, at his second coming to judge the world, v. 27. If we look to the end of all these things, the period of the world, and the posture of souls then, we shall thence form a very different idea of the present state of things. If we see things as the will appear then, we shall see them as they should appear now.The great encouragement to steadfastness in religion is taken from the second coming of Christ, considering it,[1.] As his honour; The Son of man shall come in the glory of his Father, with his angels. To look upon Christ in his state of humiliation, so abased, so abused, a reproach of men, and despised of the people, would discourage his followers from taking any pains, or running any hazards for him; but with an eye of faith to see the Captain of our salvation coming in his glory, in all the pomp and power of the upper world, will animate us, and make us think nothing too much to do, or too hard to suffer, or him. The Son of man shall come. He here gives himself the title of his humble state (he is the Son of man ), to show that he is not ashamed to own it. His first coming was in the meanness of his children, who being partakers of flesh, he took part of the same; but his second coming will be in the glory of his Father. At his first coming, he was attended with poor disciples; at his second coming, he will be attended with glorious angels; and if we suffer with him, we shall be glorified with him, 2 Tim. 2:12 .[2.] As our concern; Then he shall reward every man according to his works. Observe, First, Jesus Christ will come as a Judge, to dispense rewards and punishments, infinitely exceeding the greatest that any earthly potentate has the dispensing of. The terror of men’s tribunal ch. 10:18 ) will be taken off by a believing prospect of the glory of Christ’s tribunal. Secondly, Men will then be rewarded, not according to their gains in this world, but according to their works, according to what they were and did. In that day, the treachery of backsliders will be punished with eternal destruction, and the constancy of faithful souls recompensed with a crown of life. Thirdly, The best preparative for that day is to deny ourselves, and take up our cross, and follow Christ; for so we shall make the Judge our Friend, and these things will then pass well in the account. Fourthly, The rewarding of men according to their works is deferred till that day. Here good and evil seem to be dispensed promiscuously; we see not apostasy punished with immediate strokes, nor fidelity encouraged with immediate smiles, from heaven; but in that day all will be set to rights. Therefore judge nothing before the time, 2 Tim. 4:6-8 .(2.) The near approach of his kingdom in this world, v. 28. It was so near, that there were some attending him who should live to see it. As Simeon was assured that he should not see death till he had seen the Lord’s Christ come in the flesh; so some here are assured that they shall not taste death (death is a sensible thing, its terrors are seen, its bitterness is tasted) till they had seen the Lord’s Christ coming in his kingdom. At the end of time, he shall come in his Father’s glory; but now, in the fulness of time, he was to come in his own kingdom, his mediatorial kingdom. Some little specimen was given of his glory a few days after this, in his transfiguration ch. 17:1 ); then he tried his robes. But this points at Christ’s coming by the pouring out of his Spirit, the planting of the gospel church, the destruction of Jerusalem, and the taking away of the place and nation of the Jews, who were the most bitter enemies to Christianity. Here was the Son of man coming in his kingdom. Many then present lived to see it, particularly John, who lived till after the destruction of Jerusalem, and saw Christianity planted in the world. Let this encourage the followers of Christ to suffer for him, [1.] That their undertaking shall be succeeded; the apostles were employed in setting up Christ’s kingdom; let them know, for their comfort, that whatever opposition they meet with, yet they shall carry their point, shall see of the travail of their soul. Note, It is a great encouragement to suffering saints to be assured, not only of the safety, but of the advancement of Christ’s kingdom among men; not only notwithstanding their sufferings, but by their sufferings. A believing prospect of the success of the kingdom of grace, as well as of our share in the kingdom of glory, may carry us cheerfully through our sufferings. [2.] That their cause shall be pleaded; their deaths shall be revenged, and their persecutors reckoned with. [3.] That this shall be done shortly, in the present age. Note, The nearer the church’s deliverances are, the more cheerful should we be in our sufferings for Christ. Behold the Judge standeth before the door. It is spoken as a favour to those that should survive the present cloudy time, that they should see better days. Note, It is desirable to share with the church in her joys, Dan. 12:12 . Observe, Christ saith, Some shall live to see those glorious days, not all; some shall enter into the promised land, but others shall fall in the wilderness. He does not tell them who shall live to see this kingdom, lest if they had known, they should have put off the thoughts of dying, but some of them shall; Behold, the Lord is at hand. The Judge standeth before the door; be patient, therefore, brethren."

Lord Jesus, I am overwhelmed by this lesson.  Grant me a heart and mind to understand and embrace fully the mystery of the cross.