Exodus 11:4-7

4Moses said, “Thus says the Lord: ‘About midnight I will go throughout Egypt,

5and all the firstborn in the land of Egypt will die, from the firstborn son of Pharaoh who sits on his throne, to the firstborn son of the slave girl who is at her hand mill, and all the firstborn of the cattle.

6There will be a great cry throughout the whole land of Egypt, such as there has never been, nor ever will be again.

7But against any of the Israelites not even a dog will bark against either people or animals, so that you may know that the Lord distinguishes between Egypt and Israel.’