Exodus 11:3-5

American Standard Version

³ And Jehovah gave the people favor in the sight of the Egyptians. Moreover the man Moses was very great in the land of Egypt, in the sight of Pharaoh’s servants, and in the sight of the people.

⁴ And Moses said, Thus saith Jehovah, About midnight will I go out into the midst of Egypt: ⁵ and all the first-born in the land of Egypt shall die, from the first-born of Pharaoh that sitteth upon his throne, even unto the first-born of the maid-servant that is behind the mill; and all the first-born of cattle.