Pharaoh and all that opposed the wishes of the first-born were of the opinion that the loss of so inconsiderable a percentage of the population was a matter of small moment. They were mistaken in their calculation, for the Divine decree included not only the first-born sons, but also the first-born daughters, and not only the first-born of the marriages then existing, but also the first-born issuing from previous alliances of the fathers and the mothers, and as the Egyptians led dissolute lives, it happened not rarely that each of the ten children of one woman was the first-born of its father.
Finally, God decreed that death should smite the oldest member of every household, whether or not he was the first-born of his parents. What God resolves is executed. At the exact instant marking the middle of the night, so precise that only God Himself could determine and discern it, He appeared in Egypt, attended by nine thousand myriads of the Angels of Destruction who are fashioned some of hail and some of flames, and whose glances drive terror and trembling to the heart of the beholder.
These angels were about to precipitate themselves into the work of annihilation, but God restrained them, saying, "My wrath will not be appeased until I Myself execute vengeance upon the enemies of Israel."