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.
- Exodus 12:13
The blood of the lamb was a sign of their faith
Belief + Action + Confidence = Faith
17 In the same way, faith by itself, if it is not accompanied by action, is dead.
- James 2:17
The blood of the lamb was a sign of promise for their future
29 The next day John saw Jesus coming toward him and said, “Look, the Lamb of God, who takes away the sin of the world!
- John 1:29