"Tell the whole congregation of Israel that on the tenth of this month they are to take a lamb for each family, a lamb for each household....You shall keep it until the fourteenth day of this month; then the whole assembled congregation of Israel shall slaughter it at twilight. They shall take some of the blood and put it on the two doorposts and the lintel of the houses in which they eat it....This is how you shall eat it: your loins girded, your sandals on your feet, and your staff I your hand; ad you shall eat it hurriedly. This is the passover of the Lord. For I will pass through the land of Egypt that night, and I will strike down every firstborn in the land of Egypt, both human beings and animals; on all the gods of Egypt I will execute judgements: I am the Lord. The blood shall be a sign or you on the houses where you live: when I see the blood, I will pass over you, and no plague shall destroy you when I strike the land of Egypt."
_________- The Bible

Taken from the Book of Exodus chapter 12 verse 3 to 13, the passage gives the advice that God gave to the Israelites for the final plague that will be upon Egypt. This is the final and most destructive plague of God to free His people from the land of Egypt and take them to the land of Canaan. as he had promised.

The Lord God advised the people to prepare themselves for the twelfth plague that He will inflict upon the people of Egypt. This final plague will kill the first-born of every living thing in Egypt, be it animals or human, including that the king Pharaoh. He told them to smear the lamb blood on their doorposts so that when the angel of death come to strike, he will skip wherever the blood is smeared. This way, the people of Israel will be saved from the massacre. He also gave them instructions on how to eat, and be ready to move out of the land of Egypt. This also became the start of the Passover festival, a reminder of God's grace and kindness to His people. The final plague will also make the Pharaoh let the Israelites leave, from which will begin the exodus of God's people for their land.