Deuteronomy 23:21-23 - Keeping Vows
21 "When you make a vow to the LORD your God, don't delay paying it, because the LORD your God will certainly demand payment from you, and then you will be guilty of sin. 22 But if you refrain from making a vow, then you won't be guilty. 23 Be sure you do whatever you promise, because you have given your word voluntarily to the LORD your God.