The Old Testament consistently taught to give ten percent of the first and the best. In fact, Israel was required to give tithes as well offerings, so they were really giving somewhere between 25 and 40 percent, depending upon how one exactly figures things. The point is that they gave far more than ten percent. Yet are we actually supposed to be giving twenty, thirty, or forty percent to God? Most of us would be in poverty is we had to do that. But that is just the thing: we don’t “have to” do that. We are not under obligation to give to God. Tithing is part of the Old Testament covenant and Law. It is not mentioned in the New Testament whatsoever. God is after the heart of the matter, for we are not under law but under grace. Think of it. When Abraham (Genesis 14:18-20), who lived before the Law, gave, he did it willingly and from a cheerful heart. No one, not God, an angel, or the priest Melchizedek had commanded him to do so. He just did it out of the overflowing generosity of his heart and because of his love and respect for God. There was no Law to tell him that he “had to” give.
If we live by the Law and under the Law, which we are not supposed to do, we will end up patting ourselves on the back simply because we gave our required ten percent. Works causes boasting and religious performance leads to pride. If we treat tithing like keeping the Law, we are giving ourselves reason to boast and thereby trying to become self-righteous and impress God and/or others. We must understand that giving to God is not a matter of keeping an Old Testament Law. The righteousness of the Law was fulfilled in us through Christ when we received Him in faith. The issue for us in our time is that we understand that all is God’s and none is ours. We are not supporting a priesthood or temple service, but we are to support the work of the ministry of the church as God leads, motivates, and provides. We do this not because we “have to” but because we “want to.”
For specific guidelines on determining how much we should give, please read this article.