Leviticus 27:33 (KJV)
33 He shall not search whether it be good or bad, neither shall he change it: and if he change it at all, then both it and the change thereof shall be holy; it shall not be redeemed.
Leviticus 27
Tithing: Old Covenant
In the old covenant people gave a certain percentage unto the Lord, whereas in the new covenant we give what God puts on our hearts.