The First Passover
Exodus 12:1-14 The Lord spoke to Moses and Aaron in the land of Egypt, saying, “This month shall be to you the beginning of months. It shall be the first month of the year to you Speak to all the congregation of Israel, saying, ‘On the tenth day of this month, they shall take to them every man a lamb, according to their fathers’ houses, a lamb for a household; and if the household is too little for a lamb, then he and his neighbor next to his house shall take one according to the number of the souls; according to what everyone can eat you shall make your count for the lamb. Your lamb shall be without defect, a male a year old. You shall take it from the sheep, or from the goats: and you shall keep it until the fourteenth day of the same month; and the whole assembly of the congregation of Israel shall kill it at evening. They shall take some of the blood, and put it on the two door posts and on the lintel, on the houses in which they shall eat it. They shall eat the flesh in that night, roasted with fire, and unleavened bread. They shall eat it with bitter herbs. Don’t eat it raw, nor boiled at all with water, but roasted with fire; with its head, its legs and its inner parts. You shall let nothing of it remain until the morning; but that which remains of it until the morning you shall burn with fire. This is how you shall eat it: with your belt on your waist, your shoes on your feet, and your staff in your hand; and you shall eat it in haste: it is the Lord’s Passover.
For I will go through the land of Egypt in that night, and will strike all the firstborn in the land of Egypt, both man and animal. Against all the gods of Egypt I will execute judgments: I am the Lord. The blood shall be to you for a token on the houses where you are: and when I see the blood, I will pass over you, and there shall no plague be on you to destroy you, when I strike the land of Egypt.
This day shall be to you for a memorial, and you shall keep it a feast to the Lord: throughout your generations you shall keep it a feast by an ordinance forever. . . .”
Subsequent Requirements to Partake of the Feast
Exodus 12:43,46-47 The Lord said to Moses and Aaron, “This is the ordinance of the Passover. . . . It must be eaten In one house. You shall not carry any of the meat outside of the house. Do not break any of its bones. All the congregation of Israel shall keep it. . . .”
Numbers 9:10-13 Say to the children of Israel, ‘If any man of you or of your generations is unclean by reason of a dead body, or is on a journey far away, he shall still keep the Passover to the Lord. In the second month, on the fourteenth day at evening they shall keep it; they shall eat it with unleavened bread and bitter herbs. They shall leave none of it until the morning, nor break a bone of it. According to all the statute of the Passover they shall keep it. But the man who is clean, and is not on a journey, and fails to keep the Passover, that soul shall be cut off from his people. Because he didn’t offer the offering of the Lord in its appointed season, that man shall bear his sin.
Deuteronomy 16:1-7 Observe the month of Abib, and keep the Passover to the Lord your God; for in the month of Abib the Lord your God brought you out of Egypt by night. You shall sacrifice the Passover to the Lord your God, of the flock and the herd, in the place which the Lord shall choose, to cause his name to dwell there [Jerusalem]. You shall eat no leavened bread with it. You shall eat unleavened bread with it seven days, even the bread of affliction; for you came out of the land of Egypt in haste; that you may remember the day when you came out of the land of Egypt all the days of your life. No yeast shall be seen with you in all your borders seven days; neither shall any of the flesh, which you sacrifice the first day at evening, remain all night until the morning. You may not sacrifice the Passover within any of your gates, which the Lord your God gives you; but at the place which the Lord your God shall choose, to cause his name to dwell in, there you shall sacrifice the Passover at evening, at the going down of the sun, at the season that you came out of Egypt. You shall roast and eat it in the place which the Lord your God chooses. In the morning you shall return to your tents.
(Emphasis mine.)