Deuteronomy 23:21-23

New Century Version

²¹ If you make a promise to give something to the Lord your God, do not be slow to pay it, because the Lord your God demands it from you. Do not be guilty of sin. ²² But if you do not make the promise, you will not be guilty. ²³ You must do whatever you say you will do, because you chose to make the promise to the Lord your God.