Exod 23:14-17

The Annual Festivals 14Three times in the year you shall hold a festival for me.15You shall observe the festival of unleavened bread; as I commanded you, you shall eat unleavened bread for seven days at the appointed time in the month of Abib, for in it you came out of Egypt. No one shall appear before me empty-handed.16You shall observe the festival of harvest, of the first fruits of your labor, of what you sow in the field. You shall observe the festival of ingathering at the end of the year, when you gather in from the field the fruit of your labor.17Three times in the year all your males shall appear before the Lord GOD.