Under the Law of Moses, God gave Israel three special feasts for which they were to assemble.
With Israel’s calendar, GOD prescribed three special feasts at specific times of the year, during which times Israel was expected to appear before GOD, eventually in Jerusalem.
The Law of Moses reads:
14 Keep a feast to Me three times in the year: 15 You shall keep the Feast of Unleavened Bread (you shall eat unleavened bread seven days, as I commanded you, at the time appointed in the month of new grains, for in it you came out of Egypt; none shall appear before Me empty); 16 and the Feast of Harvest, the first fruits of your labors you sowed in the field; and the Feast of Ingathering at the end of the year, when you gather in the fruit of your labors from the field. 17 Three times in the year all your males shall appear before the Lord your God.Exodus 23:14-17 OSB
Later, Moses recapped the Law in detail in Deuteronomy. There we read:
16 Three times a year all your males shall appear before the Lord your God in the place the Lord chooses; at the Feast of Unleavened Bread, at the Feast of Weeks, and at the Feast of Tabernacles; and they shall not appear before the Lord your God empty-handed. 17 Every man shall give as he is able, according to the blessing the Lord your God gave you.Deuteronomy 16:16-17 OSB
So the three special feasts were:
- Passover and the Feast of Unleavened Bread
- Feast of Weeks (Harvest or Firstfruits, and eventually, Pentecost)
- Feast ofTabernacles (Booths, eventually, Rosh Hashanah)