Exodus 11:5-7

Revised Standard Version

⁵ and all the first-born in the land of Egypt shall die, from the first-born of Pharaoh who sits upon his throne, even to the first-born of the maidservant who is behind the mill; and all the first-born of the cattle. ⁶ And there shall be a great cry throughout all the land of Egypt, such as there has never been, nor ever shall be again. ⁷ But against any of the people of Israel, either man or beast, not a dog shall growl; that you may know that the Lord makes a distinction between the Egyptians and Israel.