Deuteronomy 16:16-17

16:16 Three times a year all your males must appear before the Lord your God in the place he chooses for the Festival of Unleavened Bread, the Festival of Weeks, and the Festival of Temporary Shelters; and they must not appear before him empty-handed. 16:17 Every one of you must give as you are able, according to the blessing of the Lord your God that he has given you.