Deuteronomy 16:16-17

Three times in a year shall all thy males appear before Jehovah 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 Jehovah empty: every man shall give as he is able, according to the blessing of Jehovah thy God which he hath given thee.