A: Exodus chapter 12 tells us how the First Passover was observed. The final plague on the Egyptians - the slaying of the Firstborn - was to happen that night. The Israelites were to sacrifice at twilight a one-year-old lamb or a goat with no defects and spread the blood on the doorposts as a sign to the Death Angel. When the Death Angel saw the blood, he would "Pass over" that house.

The meat of the animal was to be roasted, and it had to be eaten completely inside the house. They could not take the meat outside the house or break any of the bones. If anything was left over, it had to be burned before morning. They were to eat it "in haste" "with your cloak tucked into your belt, your sandals on your feet and your staff in your hand." In other words, ready to hit the road, because as soon as they got the word from Pharaoh to leave Egypt, they had to be ready to go. They also ate unleavened bead, because there was no time for bread to rise. (Deuteronomy 16:3) After they had left, God told Moses to have observe that date every year by removing all the leaven from their homes and eating only unleavened bread for seven days.

While they were wandering in the wilderness, some of the people came in contact with a dead body and became ceremonially unclean, making them ineligible to eat the Passover. Moses had to ask God what to do. God told them to wait until the second month and eat the Passover then, with unleavened bread and bitter herbs. This "second chance" Passover was good for people who had become unclean or were away on a Journey, but could not be used by anyone else. (Numbers 9:1-14)