Exodus 11:4-7

Moses had announced to Pharaoh, “This is what the LORD says: At midnight tonight I will pass through the heart of Egypt. All the firstborn sons will die in every family in Egypt, from the oldest son of Pharaoh, who sits on his throne, to the oldest son of his lowliest servant girl who grinds the flour. Even the firstborn of all the livestock will die. Then a loud wail will rise throughout the land of Egypt, a wail like no one has heard before or will ever hear again. But among the Israelites it will be so peaceful that not even a dog will bark. Then you will know that the LORD makes a distinction between the Egyptians and the Israelites.