Sahih al-Bukhari 4051
Narrated Jabir:
This Verse: "When two of your parties almost Decided to fall away..." was revealed in our connection, 
i.e. Bani Salama and Bani Haritha and I would not have liked that, if it was not revealed, for Allah 
said:-- But Allah was their Protector.....(3.122)
حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، عَنِ ابْنِ عُيَيْنَةَ، عَنْ عَمْرٍو، عَنْ جَابِرٍ ـ رضى الله عنه ـ قَالَ نَزَلَتْ هَذِهِ الآيَةُ فِينَا ‏{‏إِذْ هَمَّتْ طَائِفَتَانِ مِنْكُمْ أَنْ تَفْشَلاَ‏}‏ بَنِي سَلِمَةَ وَبَنِي حَارِثَةَ، وَمَا أُحِبُّ أَنَّهَا لَمْ تَنْزِلْ، وَاللَّهُ يَقُولُ ‏{‏وَاللَّهُ وَلِيُّهُمَا‏}‏