This passage gives the historical reason and setting for the feast of the Passover. God saved Israel from Egyptian slavery when the angel of death passed over the homes of Israel and killed the children of the Egyptians. Every year they thanked the Lord for this miracle of favoritism for his chosen people.
A lamb was given in sacrifice for their sins and for this miracle. Jesus became the last lamb to be sacrificed for his people -- for all who believed in him! He was the perfect lamb without defect. He had no sin in him. We are all children of Abraham through faith in Christ.