For the LORD will pass through to strike the Egyptians, and when he sees the blood on the lintel and on the two doorposts, the LORD will pass over the door and will not allow the destroyer to enter your houses to strike you.
23. For the Lord will pass through. He forbids them to go out during the night, lest they should mix themselves with the Egyptians, but commands them to keep quietly under the protection of the blood. By this sign they were admonished that they also were exposed to destruction, if they did not separate themselves from the unbelievers under the safeguard of the blood.
Moses faithfully taught the elders all God had commanded him. The people must not stir out of doors that night, staying under the protection of the blood; their safety hangs on the sprinkled mark, not on their own wisdom or strength. Later they must teach their children what this service means.
AI summary
Commenting on Exodus 12:21-28
For the Lord will pass though to smite the Egyptians,.... All the firstborn in the several families, in all the towns and cities in Egypt: and when he seeth the blood upon the lintel, and upon the two side posts; which must be understood of his taking notice of it with a special view to the good of those within the house; otherwise every thing...