Deuteronomy 16:1-17 (NRSV)
16 Observe the month of Abib by keeping the passover to the Lord your God, for in the month of Abib the Lord your God brought you out of Egypt by night. 2 You shall offer the passover sacrifice to the Lord your God, from the flock and the herd, at the place that the Lord will choose as a dwelling for his name. 3 You must not eat with it anything leavened. For seven days you shall eat unleavened bread with it—the bread of affliction—because you came out of the land of Egypt in great haste, so that all the days of your life you may remember the day of your departure from the land of Egypt. 4 No leaven shall be seen with you in all your territory for seven days; and none of the meat of what you slaughter on the evening of the first day shall remain until morning. 5 You are not permitted to offer the passover sacrifice within any of your towns that the Lord your God is giving you. 6 But at the place that the Lord your God will choose as a dwelling for his name, only there shall you offer the passover sacrifice, in the evening at sunset, the time of day when you departed from Egypt. 7 You shall cook it and eat it at the place that the Lord your God will choose; the next morning you may go back to your tents. 8 For six days you shall continue to eat unleavened bread, and on the seventh day there shall be a solemn assembly for the Lord your God, when you shall do no work.
9 You shall count seven weeks; begin to count the seven weeks from the time the sickle is first put to the standing grain. 10 Then you shall keep the festival of weeks to the Lord your God, contributing a freewill offering in proportion to the blessing that you have received from the Lord your God. 11 Rejoice before the Lord your God—you and your sons and your daughters, your male and female slaves, the Levites resident in your towns, as well as the strangers, the orphans, and the widows who are among you—at the place that the Lord your God will choose as a dwelling for his name. 12 Remember that you were a slave in Egypt, and diligently observe these statutes.
13 You shall keep the festival of booths for seven days, when you have gathered in the produce from your threshing floor and your wine press. 14 Rejoice during your festival, you and your sons and your daughters, your male and female slaves, as well as the Levites, the strangers, the orphans, and the widows resident in your towns. 15 Seven days you shall keep the festival to the Lord your God at the place that the Lord will choose; for the Lord your God will bless you in all your produce and in all your undertakings, and you shall surely celebrate.
16 Three times a year all your males shall appear before the Lord your God at the place that he will choose: at the festival of unleavened bread, at the festival of weeks, and at the festival of booths. They shall not appear before the Lord empty-handed; 17 all shall give as they are able, according to the blessing of the Lord your God that he has given you.