Deuteronomy 16:10

Then you shall keep the Feast of Weeks to the Lord your God with the tribute of a freewill offering from your hand , which you shall give as the Lord your God blesses you.

Then celebrate the Festival of Weeks to the Lord your God by giving a freewill offering in proportion to the blessings the Lord your God has given you.

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: