So when they had despaired of him, they secluded themselves in private consultation. The eldest of them said, "Do you not know that your father has taken upon you an oath by Allāh and [that] before you failed in [your duty to] Joseph? So I will never leave [this] land until my father permits me or Allāh decides for me,1 and He is the best of judges.
Translation: Saheeh International (English)
1 i.e., in my favor by bringing about the release of Benjamin.
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.