Deuteronomy 16:1, 10, 13

Observe the month of Abib, and keep the passover unto the LORD thy God: for in the month of Abib the LORD thy God brought thee forth out of Egypt by night.

And thou shalt keep the feast of weeks unto the LORD thy God with a tribute of a freewill offering of thine hand, which thou shalt give unto the LORD thy God, according as the LORD thy God hath blessed thee

Thou shalt observe the feast of tabernacles seven days, after that thou hast gathered in thy corn and thy wine