Deuteronomy 23:19-21

New Revised Standard Version, Anglicised Catholic Edition

¹⁹ You shall not charge interest on loans to another Israelite, interest on money, interest on provisions, interest on anything that is lent. ²⁰ On loans to a foreigner you may charge interest, but on loans to another Israelite you may not charge interest, so that the Lord your God may bless you in all your undertakings in the land that you are about to enter and possess.

²¹ If you make a vow to the Lord your God, do not postpone fulfilling it; for the Lord your God will surely require it of you, and you would incur guilt.