Deuteronomy 23:21-23

Revised Standard Version

²¹ “When you make a vow to the Lord your God, you shall not be slack to pay it; for the Lord your God will surely require it of you, and it would be sin in you. ²² But if you refrain from vowing, it shall be no sin in you. ²³ You shall be careful to perform what has passed your lips, for you have voluntarily vowed to the Lord your God what you have promised with your mouth.