Exodus 11:4-7

4Moses said, “This is what the Lord says: About midnight I will go out among the Egyptians.

5Every firstborn son in Egypt will die, from the firstborn of Pharaoh who rules the land, to the firstborn children of female slaves who use their handmills, including every firstborn domestic animal.

6There will be loud crying throughout Egypt, such as there has never been or ever will be again.

7But where the Israelites are, not even a dog will be startled by any person or animal. This is how you will see that the Lord shows the distinction between Egypt and Israel.