Deuteronomy 16:16-17

16 ¶ Three times in a year shall all thy males appear before the Lord thy God in the place which he shall choose; in the feast of unleavened bread, and in the feast of weeks, and in the feast of tabernacles: and they shall not appear before the Lord empty: 17 Every man shall give as he is able, according to the blessing of the Lord thy God which he hath given thee.