Deuteronomy 23:21-23

New Catholic Bible

²¹ You can charge a foreigner interest, but you cannot charge a brother interest. For this you will be blessed by the Lord, your God, in everything that you undertake in the land that you are entering to possess.

²² If you make a vow to the Lord, your God, do not be lax in paying it off, for the Lord, your God, will certainly require it of you, and you would be guilty of a sin. ²³ But if you fail to make a vow, there is no sin.