Deuteronomy 16:1, 10, 13

Observe the month of Aviv and celebrate the Passover of the LORD your God, because in the month of Aviv he brought you out of Egypt by night.

Then celebrate the Festival of Weeks to the LORD your God by giving a freewill offering in proportion to the blessings the LORD your God has given you.

Celebrate the Festival of Tabernacles for seven days after you have gathered the produce of your threshing floor and your winepress.