Exodus 12:13

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 30:12

30:12 “When you take a census of the Israelites according to their number, then each man is to pay a ransom for his life to the Lord when you number them, so that there will be no plague among them when you number them.