Being treated as spies and roughly so, Joseph's brothers, who had attempted to kill him, but sold him into slavery and lied to their father, come to acknowledge their sin. Simeon, the oldest, whose job it was to protect Joseph, is held in prison as a hostage to test them. It is through this that they begin to come to repentance. Recognizing our sin, which sometimes comes only as through punishment, is the beginning of repentance.