11 Oct Deuteronomy 23:21-23

21 “When you make a vow to the Lord your God, be prompt in fulfilling whatever you promised him. For the Lord your God demands that you promptly fulfill all your vows, or you will be guilty of sin. 22 However, it is not a sin to refrain from making a vow. 23 But once you have voluntarily made a vow, be careful to fulfill your promise to the Lord your God.