Charles Spurgeon Commentary Exodus 12:13

"And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and there shall no plague be upon you to destroy you, when I smite the land of Egypt." — Exodus 12:13 (ASV)

And the blood shall be to you for a token upon the houses where you are:

Oh that we would all look upon the blood of Jesus as a token: a token of divine love in giving the Well-beloved to die for us; a token that justice has had its due; a token that we are perfectly secure forever!

And when I see the blood, I will pass over you,

It is God's view of the blood of Christ which is the all-important matter; when He looks at Christ upon the cross and is satisfied with the atonement that He there offered, the Lord passes over all those for whom Christ died as a Substitute.