'Freewill Offering' in the Bible

You are to bring there your burnt offerings and sacrifices, your tenths and personal contributions, your vow offerings and freewill offerings, and the firstborn of your herds and flocks.

Within your gates you may not eat: the tenth of your grain, new wine, or oil; the firstborn of your herd or flock; any of your vow offerings that you pledge; your freewill offerings; or your personal contributions.

You are to celebrate the Festival of Weeks to the Lord your God with a freewill offering that you give in proportion to how the Lord your God has blessed you.