Exodus 12:12-13

12:12 I will pass through the land of Egypt in the same night, and I will attack all the firstborn in the land of Egypt, both of humans and of animals, and on all the gods of Egypt I will execute judgment. I am the Lord. 12:13 The blood will be a sign for you on the houses where you are, so that when I see the blood I will pass over you, and this plague will not fall on you to destroy you when I attack the land of Egypt.

Exodus 12:29-30

The Deliverance from Egypt

12:29 It happened at midnight – the Lord attacked all the firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the captive who was in the prison, and all the firstborn of the cattle. 12:30 Pharaoh got up in the night, along with all his servants and all Egypt, and there was a great cry in Egypt, for there was no house in which there was not someone dead.