Exodus 11:4-7

4And Moses said, Thus saith Jehovah: About midnight I will go out into the midst of Egypt.

5And all the firstborn in the land of Egypt shall die, from the firstborn of Pharaoh who sitteth on his throne, even unto the firstborn of the bondwoman that is behind the mill; and all the firstborn of cattle.

6And there shall be a great cry throughout 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 that Jehovah distinguisheth between the Egyptians and Israel.