From Saint John Chrysostom on how the blood of Christ sanctifies our lips, just as the blood of the passover lamb sanctified and protected the homes of the Hebrews:
If we wish to understand the power of Christ’s blood, we should go back to the ancient account of its prefiguration in Egypt.Interested in learning more? Listen to Jewish Passover, Catholic Mass Podcast (Give it a few seconds depending on the breadth of your internet connection.)
“Sacrifice a lamb without blemish,” commanded Moses, “and sprinkle its blood on your doors.”
If we were to ask him what he meant, and how the blood of an irrational beast could possibly save men endowed with reason, his answer would be that the saving power lies not in the blood itself, but in the fact that it is a sign of the Lord’s blood. In those days, when the destroying angel saw the blood on the doors he did not dare to enter, so how much less will the devil approach now when he sees, not that figurative blood on the doors, but the true blood on the lips of believers, the doors of the temple of Christ.
-Saint John Chrysostom, Catecheses