Genesis 44:17
And he said, God forbid that I should do so: but the man in whose hand the cup is found, he shall be my servant; and as for you, get you up in peace unto your father. And he said, God forbid that I should do so: but the man in whose hand the cup is found, he shall be my servant; and as for you, get you up in peace unto your father.
Joseph refused Judah's offer to keep all the brothers as his servants, ruling that only the man in whose hand the cup was found should remain as his servant while the rest should go up in peace to their father. That ruling singled out Benjamin as the one to be held, leaving the others free to return safely to their father. The declaration was a deliberate test designed to reveal the brothers' true feelings and to prove their concern for Benjamin and for their father. It was meant to draw from them an acknowledgment of their past wrong course.
The test brought Judah to plead for Benjamin and to offer himself as a servant in Benjamin's place. He asked to stay as a substitute slave so that Benjamin might go free. His plea rested on the fact that his father's life was bound up with the lad's life, and he was unwilling to go back without him and bring grief upon his father.
In connection with the cup incident Joseph claimed no power of divination for himself. Yet he was willing for his brothers to believe that he could read the secret acts of their lives.