Deuteronomy 23:23 KJV
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.
Deuteronomy 23:23, King James Version
In context
22 But if thou shalt forbear to vow, it shall be no sin in thee.
23 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.
24 When thou comest into thy neighbour’s vineyard, then thou mayest eat grapes thy fill at thine own pleasure; but thou shalt not put any in thy vessel.