Exodus 12:1-14 details God's instructions to the Israelites regarding the first Passover, which event would mark the beginning of their deliverance from Egyptian oppression. The Passover would not only commemorate the deliverance of the Israelites from slavery, but also foreshadowed Jesus's death on the cross for sinners. The Passover was to be such a significant event in the Israelites' lives that God commanded that the Israelites change the beginning of the calendar year to coincide with the Passover. (v. 2)
On the tenth day of the month God instructed the Israelites to select an animal to be sacrificed at Passover. It was important that the animal be the right size so each member of the household had an adequate portion. If a family was small, they could join with another family to share an animal. (v. 3-4) While God wanted everyone to participate in the Passover feast, He did not want the Israelites to be wasteful and sacrifice an animal that could not be consumed by a family. The animal could have been either a goat or a sheep, and it must be an unblemished animal, that is without defect. The animal also had to be a year old. (v. 5) God gave us His best, His one and only Son, Jesus Christ, who was spotless, that is without same. Accordingly, God expects our best when we worship Him and to give him our second best is in insult to Him.
Once the animal was selected, it was to be separated from the flock and tended to by the Israelites for four days until the fourteenth day of the same month, which would be the day that the animal would be killed at twilight. (v. 6) Blood from the animal was to be placed on both doorposts and above the door of the house where the animal was to eaten. (v. 7)
Then the animal was to be roasted so the family could eat it that night along with unleavened bread and bitter herbs. (v. 8-9) Roasting provided a quick means to cook the animal and would make it possible to cook the whole animal all at one time. To use leavening in the bread to make it rise would take time, but also, symbolically the leavening agent represents sin. The way of cooking the animal and preparing the bread that God gave the Israelites were quick methods and was to create a sense of urgency. The Israelites did not have time for a long, elaborate meal because God would soon deliver them for Egypt, and they had to be ready to leave. Also, the bitter herbs could be found quickly and symbolically they were to represent the bitter times experienced by the Israelited in captivity.
Any leftovers from the meal were to be burned. (v. 10) God did not tell the Israelites to pack the food for the journey, but they were instead to trust God to provide nourishment for them after they left Egypt. Another demonstration of their faith was that the Israelites were to eat the meal dressed ready for travel and to eat the meal in a hurry. (v. 11)
On the night that the first Passover was observed, God told the Israelites that He would pass through the land of Egypt, and every firstborn male, both man and animal, would die. (v. 12) God would be executing His judgment against all of the Egyptian gods while exhibiting grace toward the Israelites and sparing them from the same fate. It would also show God's sovereignty and the impotency of the Egyptians' gods. The blood that the Israelites would place on the door frame would be a sign distinguishing them from the Egyptians and God said that "when I see the blood, I will pass over you". God did not need the blood on the door frame of the Israelites' homes to identify them; He knew who His people were and where they were. Rather the blood was a sign of the Israelites' faith and obedience to God.
God instructed the Israelites to celebrate Passover each year as a way to remember what God had done for them and to show their love, thankfulness and obedience to God. (v. 14) The annual observance of Passover would also be a way to teach future generations of God's deliverance of the Israelites.