Exodus 23:14-17

14Three times thou shalt keep a feast unto me in the year. 15The feast of unleavened bread shalt thou keep: seven days thou shalt eat unleavened bread, as I commanded thee, at the time appointed in the month Abib (for in it thou camest out from Egypt); and none shall appear before me empty: 16and the feast of harvest, the first-fruits of thy labors, which thou sowest in the field: and the feast of ingathering, at the end of the year, when thou gatherest in thy labors out of the field. 17Three times in the year all thy males shall appear before the Lord Jehovah.