Genesis 42:8

By them. Years and change of situation, had made such an alteration in him. God was pleased that Jacob should remain so long ignorant of his son's fate, that, by sorrow, he might do penance, and purify himself from every stain; and that he might not attempt to redeem Joseph, whose slavery was to be the source of so much good to his family. (Menochius) --- Joseph did not make himself known at first; in order to bring his brethren to a true sense of their duty, that they might obtain pardon for their sin. Thus pastors must sometimes treat their penitents with a degree of severity. (St. Gregory, hom. 22, Ezec.; St. Augustine, ser. 82, de Tem.) (Worthington)