Exodus 23:15-17 Revised Standard Version (RSV)
15 You shall keep the feast 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. None shall appear before me empty-handed. 16 You shall keep the feast of harvest, of the first fruits of your labor, of what you sow in the field. You shall keep the feast of ingathering at the end of the year, when you gather in from the field the fruit of your labor. 17 Three times in the year shall all your males appear before the Lord God.