Exodus 12:12

For. will pass through Egypt this night.

This explains how the blood of the lamb was the Lord's Passover. He would pass in wrath through Egypt, but pass over the homes of Israel where the blood of the lamb was sprinkled on the door post. The word rendered "pass through" is wholly distinct from that which means "pass over." The passing through was in judgment, the passing over in mercy.-- Canon Cook.

Man and beast.

The helpless brute creation must unconsciously bear the yoke of sin, and suffer with their erring masters.

Against all the gods of Egypt.

The slaying of the first-born was. judgment upon the gods, not only because the impotence and worthlessness of the fancied gods were displayed in the consternation by this stroke, but still more directly in the death of the king's first-born son, and many first-born animals that were worshiped as gods.