Darkness was the penultimate plague: And Moses stretched out his hand over the heavens and there was pitch-dark in all the land of Egypt three days. No one saw his fellow and no one rose from where he was three days, but all the Israelites had light in their dwelling places. Why could nobody see his fellow? Because no one rose from where he was. The unwillingness to move beyond “their place,” to see things from the perspective of someone else, was leading Egypt to destruction. And why did Israel have light? Because they were unified and looked out for another, all the Israelites had light, when we include everyone, explains R. Shmuel of Slonim, then we bring light into the world.