Those among the Egyptians who gave credence to Moses' words, and tried to shield their first-born children from death, sent them to their Hebrew neighbors, to spend the fateful night with them, in the hope that God would exempt the houses of the children of Israel from the plague. But in the morning, when the Israelites arose from their sleep, they found the corpses of the Egyptian fugitives next to them. That was the night in which the Israelites prayed before lying down to sleep: "Cause us, O Lord our God, to lie down in peace, remove Satan from before us and from behind us, and guard our going out and our coming in unto life and unto peace," for it was Satan that had caused frightful bloodshed among the Egyptians.
Signs and Wonders of Moses of Egyptians
Legends of the Jews 4:333