Deuteronomy 16:10 And thou shalt keep the feast of weeks unto the Lord thy God with a tribute of a freewill offering of thine hand, which thou shalt give unto the Lord thy God, according as the Lord thy God hath blessed thee: 10 I MC VC

Deuteronomy 23:23 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. 12 I MC VC