Exodus 11:4-7

4And Moses said, Thus saith the LORD, About midnight will I go out into the midst of Egypt: 5And all the firstborn in the land of Egypt shall die, from the firstborn of Pharaoh that sitteth upon his throne, even to the firstborn of the maidservant that is behind the mill; and all the firstborn of beasts. 6And there shall be a great cry throughout all the land of Egypt, such as there hath been none like it, nor shall be like it any more. 7But against any of the children of Israel shall not a dog move his tongue, against man or beast: that ye may know how the LORD doth put a difference between the Egyptians and Israel.