Thus saith the LORD, About midnight will I go out into the midst of Egypt:
And all the firstborn in the land of Egypt shall die, from the first born of Pharaoh that sitteth upon his throne, even unto the firstborn of the maidservant that is behind the mill; and all the firstborn of beasts. Exodus 11:4-5
I will pass through the land of Egypt this night, and will smite all the firstborn in the land of Egypt, both man and beast. Exodus 12:12
And it came to pass, that at midnight the LORD smote all the firstborn in the land of Egypt, from the firstborn of Pharaoh that sat on his throne unto the firstborn of the captive that was in the dungeon; and all the firstborn of cattle.
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. Exodus 12:29-30