So when they had despaired of him, they secluded themselves in private (12:80)

﴿فَلَمَّا اسْتَيْأَسُوا مِنْهُ خَلَصُوا نَجِيًّا ۖ قَالَ كَبِيرُهُمْ أَلَمْ تَعْلَمُوا أَنَّ أَبَاكُمْ قَدْ أَخَذَ عَلَيْكُم مَّوْثِقًا مِّنَ اللَّهِ وَمِن قَبْلُ مَا فَرَّطتُمْ فِي يُوسُفَ ۖ فَلَنْ أَبْرَحَ الْأَرْضَ حَتَّىٰ يَأْذَنَ لِي أَبِي أَوْ يَحْكُمَ اللَّهُ لِي ۖ وَهُوَ خَيْرُ الْحَاكِمِينَ﴾
[ يوسف: 80]

12:80 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 Allah and [that] before you failed in [your duty to] Joseph? So I will never leave [this] land until my father permits me or Allah decides for me, and He is the best of judges.

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.

So, when they despaired of him, they held a conference in private. The eldest among them said: "Know you not that your father did take an oath from you in Allah's Name, and before this you did fail in your duty with Yusuf (Joseph)? Therefore I will not leave this land until my father permits me, or Allah decides my case (by releasing Benjamin) and He is the Best of the judges.

phonetic Transliteration

Falamma istayasoo minhu khalasoo najiyyan qala kabeeruhum alam taAAlamoo anna abakum qad akhatha AAalaykum mawthiqan mina Allahi wamin qablu ma farrattum fee yoosufa falan abraha alarda hatta yathana lee abee aw yahkuma Allahu lee wahuwa khayru alhakimeena

Abdullah Yusuf Ali - Translation

Now when they saw no hope of his (yielding), they held a conference in private. The leader among them said: "Know ye not that your father did take an oath from you in Allah's name, and how, before this, ye did fail in your duty with Joseph? Therefore will I not leave this land until my father permits me, or Allah commands me; and He is the best to command.

Safi-ur-Rahman al-Mubarakpuri

So, when they despaired of him, they consulted in private. The eldest among them said: "Know you not that your father did take an oath from you in Allah's Name, and before this you did fail in your duty with Yusuf Therefore I will not leave this land until my father permits me, or Allah decides my case and He is the Best of the judges.

Page 245 English transliteration