Yusuf · 12:80

80. When they despaired of Joseph responding to their request, they went away from the people to consult with each other. Their oldest brother asked them if they remembered that their father had taken a firm promise in the name of Allah from them that they would return his son to him, unless they were completely overwhelmed by what they were unable to repel, and that before that they had failed with regards to Joseph, and had not kept their promise to their father concerning him. He said that he would not leave the land of Egypt until his father permitted him to return to him, or Allah decreed that he take his brother back. Allah is the Best of Judges, judging with truth and justice.