Exodus 10:23

But the children of Israel had light in their dwellings — Not only in the land of Goshen, where most of them inhabited, but in the particular dwellings which in other places the Israelites had dispersed among the Egyptians, as it appears they had by the distinction afterwards appointed to be put on their door — posts. And during these three days of darkness to the Egyptians, if God had so pleased, the Israelites by the light which they had, might have made their escape, and have asked Pharaoh no leave; but God would bring them out with a high hand, and not by stealth or in haste.