Deuteronomy 23:21-23

New International Version - UK

²¹ If you make a vow to the Lord your God, do not be slow to pay it, for the Lord your God will certainly demand it of you and you will be guilty of sin. ²² But if you refrain from making a vow, you will not be guilty. ²³ Whatever your lips utter you must be sure to do, because you made your vow freely to the Lord your God with your own mouth.