Bring the whole tithe into the storehouse

"Bring the whole tithe into the storehouse, That there may be food in my house. Put me to the test, says the LORD of hosts, And see if I do not open the floodgates of heaven for you, and pour down upon you blessing without measure!" (Malachi 3: 10)

God owns everything. 

“Blessed are you, Lord God of all creation.  Through your goodness I have this gift to offer, the fruit of the earth and the work of my hands.  let it become for me like the bread of life.”  This is a paraphrase of the Offertory prayer.  It teaches us that the gifts we bring to the altar come from God.  God gives the inspiration and the power to act.  We can never outdo God in generosity.