2 Corinthians 9:7 - Every man according as he purposeth in his heart, [so let him give]; not grudgingly, or of necessity: for God loveth a cheerful giver.
Why do people tithe to the church? The reasons are many.
God owns the entire world and its substance. "The earth is the LORD'S, and the fullness thereof" (Psalm 24:1). "Behold, all souls are mine" (Ezekiel 18:4). "The silver is mine, and the gold is mine" (Haggai 2:8). It is God who gives people the power to obtain wealth (Psalm 75:6-7; Ecclesiastes 5:19). We are not to glory in what God has given us, but to glory in Him (Jeremiah 9:23-24).
Why should I be grudge God ten percent when everything actually belongs to Him? If it were not for Him, there would be no land, no seed, no strength, no income, and no life. How generous He is to tell us, ""he tithe… is the LORD'S"! (Leviticus 27:30).