Sahih (Sahih al-Bukhari)
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}
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