In Parashat Miketz, we read that Yaakov sends his remaining sons to Egypt to purchase grain from the Egyptian vizier, who, unbeknownst to them, is none other than their missing brother, Yosef. Yosef accuses them of coming to Egypt to spy the country, and demands that they bring their youngest brother, Binyamin, as proof of their innocence. He keeps Shimon as prisoner in Egypt to guarantee the other brothers' return.
