Exodus 12:12, 29-30

For I [the LORD] will pass through the land of Egypt on this night, and will strike down all the firstborn in the land of Egypt, both man and animal; against all the gods of Egypt I will execute judgments [exhibiting their worthlessness]. I am the LORD.

Now it happened at midnight that the LORD struck every firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the prisoner who was in the dungeon, and all the firstborn of the cattle. Pharaoh got up in the night, he and all his servants and all the Egyptians, and there was a great cry [of heartache and sorrow] in Egypt, for there was no house where there was not someone dead.