The Mekhilta, the tannaitic midrash on Exodus, preserves a teaching from Rabbi Yossi HaGlili that explains why the Egyptians willingly handed over their treasures to the departing Israelites. The Torah says the Egyptians gave the Israelites whatever they asked for (Exodus 12:36), but why would a nation surrender its wealth to former slaves?
Rabbi Yossi HaGlili offers a striking psychological explanation rooted in the plague of darkness — the ninth plague, which preceded the death of the firstborn. For three days, Egypt was engulfed in a darkness so thick that no one could move. The Egyptians sat frozen in their homes while the Israelites, miraculously, had light (Exodus 10:23).
During those three days of darkness, the Israelites could see everything. They could see where the Egyptians stored their valuables. They could have taken anything they wanted — gold, silver, clothing — and the Egyptians would never have known. They were blind, immobilized, helpless.
But the Israelites took nothing. They did not steal a single item during those three days of perfect opportunity. Rabbi Yossi HaGlili says the Egyptians remembered this. When the Israelites later asked for their possessions, the Egyptians reasoned: "If they did not steal from us during the darkness — when they could easily have taken advantage of our blindness — should they be suspect now?" The Israelites had earned trust through restraint. The Egyptians gave freely because the Israelites had proven themselves honest when honesty cost them everything.