Genesis 42:18

This do, and live. On the third day Joseph modified his severe attitude. His explanation, “I fear God,” was intended to be understood in a general way, without reference to Jehovah, as supposedly coming from an Egyptian ruler. Instead of imprisoning nine of them he would keep only one in prison, and allow the others to return to fetch Benjamin and to carry food to their suffering families. Their return with Benjamin would procure the release of the one to be held in prison. If, on the other hand, they had deceived Joseph with their story, they would die of hunger, and the one remaining behind in Egypt would be executed as a spy.