"It is the LORD'S Passover. On that same night I will pass through Egypt and I will strike down every first born of both people and animals, and I will bring judgement on all the gods of Egypt, I AM The LORD".
Then several scriptures down we see, "When the LORD goes through the land to strike down the Egyptians, He will see the blood on the top and sides of the doorframe and will pass over that doorway, and He will not permit the destroyer to enter your houses and strike you down".
This reminds me of the military Gentile who saught Jesus out to heal his servant. The military man said he understands authority and when he tells his men do this or that from afar, they do it; thus, he knew Jesus could make a command right where he was standing and it would happen at the Gentiles house. He knew Jesus did not need to go there to perform this miracle. Jesus was impressed at this mans understanding of Jesus' authority over the spirits. Jesus told the destroying spirit what to do and it did it.