Deuteronomy 23:21-23

Amplified Bible, Classic Edition

²¹ When you make a vow to the Lord your God, you shall not be slack in paying it, for the Lord your God will surely require it of you, and slackness would be sin in you.

²² But if you refrain from vowing, it will not be sin in you.

²³ The vow which has passed your lips you shall be watchful to perform, a voluntary offering which you have made to the Lord your God, which you have promised with your mouth.