Not a house, to wit, of those houses which had any first-born in them, for in divers families there might be no first-born. And such restrictions of the universal particles are frequently understood.
Related Commentaries of Exodus 12:30
Exodus 12:30
30 And Pharaoh rose up in the night, he, and all his servants, and all the Egyptians; and there was a great cry in Egypt; for there was not a house where there was not one dead.