I bought a book a few months ago that I thought could be a good resource. It turned out to be a fantastic encouragement and challenged me to see Jesus’ sacrificial and substitutional work throughout the entire Bible. The book, It is Well, is a combination of sermons from Mark Dever and Michael Lawrence that will bless you and teach you as you read. Here is a section on Exodus 12:13:
“The Lord continues in verse 13: ‘The blood will be a sign for you on the houses where you are; and when I see the blood, I will pass over you. No destructive plague will touch you when I strike Egypt.’ The blood is a sign of salvation for the Israelites, but notice that it was not just the Egyptians who were subject to God’s wrath and deserved his punishment. God does not say that the Israelites were exempt from judgement just because they were Israelites, or because they lived better lives than the Egyptians. No, the Israelites themselves were under God’s wrath, and so they needed to be protected. If they would be saved, it would not be because God’s justice had no claim against them; it would be because when God saw the blood on the door frames, the blood of the sacrificial substitute, he would in grace pass over that house as he judged. Spread upon the doorframes, the blood of the lamb symbolically covered those within whose own blood rightfully should have been shed in penalty for their sins.”
Here is a section on Exodus 12:13 that points us to Jesus’ atoning work on the cross and symbolic representation of the slaughtered lamb for his people’s salvation. In this, then, we must remember the whole Bible speaks of Jesus. We would do well to read our entire Bible because it all points us to Christ Jesus. As Jesus says that even Moses wrote of him (John 5:46) and that the whole Old Testament spoke of him (Luke 24:44–46).
To close, the blood found in Exodus 12 is a sign that points towards the future and true Substitute: Jesus, whose blood is not merely a sign––it is effectual. What can wash away our sins? Nothing but the blood of Jesus. Therefore, we joyfully exclaim: “Worthy is the Lamb who was slain!”
 Mark Dever and Michael Lawrence, It is Well: Expositions on Substitutionary Atonement 9Marks (Wheaton, IL: Crossway, 2010), 19–20.