In this week's readings are two stories of sacrifice, two foreshadowings of Christ's death for us. In Genesis 22, God commands Abraham to take his son, his only son, whom he loves, and offer him as a burnt offering. As Abraham and Isaac journey together to make a sacrifice, Isaac asks where the lamb for the offering is. Abraham, in faith, answers, "God will provide for Himself the lamb for the burnt offering."
In Exodus 12, the Lord gives Moses and Aaron instructions for the Passover, that the Israelites might escape the final plague - the deaths of their firstborn sons. The blood of the sacrificed lamb is a sign and a protection for them. Inside their homes, with the blood on the doorposts, they are protected from the Lord's judgement.
In both stories, the firstborn son, the beloved son, is spared; and we are pointed to another firstborn, Beloved Son, who was not spared but who became for us our substitute sacrifice, our Passover Lamb.