Surah Yusuf 12:66

قَالَ لَنْ أُرْسِلَهُۥ مَعَكُمْ حَتَّىٰ تُؤْتُونِ مَوْثِقًا مِّنَ ٱللَّهِ لَتَأْتُنَّنِى بِهِۦٓ إِلَّآ أَن يُحَاطَ بِكُمْ ۖ فَلَمَّآ ءَاتَوْهُ مَوْثِقَهُمْ قَالَ ٱللَّهُ عَلَىٰ مَا نَقُولُ وَكِيلٌ

[Jacob] said, "Never will I send him with you until you give me a promise [i.e., oath] by Allāh that you will bring him [back] to me, unless you should be surrounded [i.e., overcome by enemies]." And when they had given their promise, he said, "Allāh, over what we say, is Entrusted."

Translation: Saheeh International

Tafsir

He said ‘I will not send him with you until you give me a solemn pledge a covenant in the name of God by your swearing an oath that assuredly you will bring him back to me unless you are besieged’ such that you die or are overwhelmed and thus unable to bring him back. They agreed to this. …

Excerpt from Tafsir al-Jalalayn, commentary on 12:66, via Quran.com. The reader has the full commentary and 9 more tafsirs.