Deuteronomy 23:23

You shall be careful to do what has passed your lips , for you have voluntarily vowed to the Lord your God what you have promised with your mouth .

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.

That which is gone out of thy lips thou shalt keep and perform; even a freewill offering, according as thou hast vowed unto the Lord thy God, which thou hast promised with thy mouth.