Exodus 12:29

And it came to pass that at midnight the Lord smote all the firstborn in the land of Egypt, from the firstborn of Pharaoh that sat on his throne unto the first-born of the captive that was in the dungeon, and all the first-born of cattle. It was a supernatural visitation, a divine punishment which was here meted out, in spite of all the attempts to explain the facts in a natural way. The very fact that the firstborn only was stricken in every case, from the highest to the lowest, shows that it could not have been a mere accident of the Egyptian pest, nor would it have struck both man and beast all in the same night.