Deuteronomy 23:21-23

21When thou vowest a vow to Jehovah thy 1God, thou shalt not delay to perform it; for Jehovah thy 2God will certainly require it of thee, and it shall be sin in thee.

22But if thou forbear to vow, it shall be no sin in thee.

23What is gone out of thy lips thou shalt keep and do, as thou hast vowed to Jehovah thy 3God, the voluntary-offering that thou hast promised with thy mouth.