Sahih Muslim 2776 a
Zaid b. Thabit reported that Allah's Apostle (ﷺ) set out for Uhud. Some of those persons who were with them came back. The Companions of Allah's Apostle (ﷺ) were divided in two groups. One group said:
We would kill them, and the other one said: No, this should not be done, and it was on this occasion that this verse was revealed:" Why should you, then, be two parties in relation to hypocrites?" (iv. 88).
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ الْعَنْبَرِيُّ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ عَدِيٍّ، - وَهُوَ
 ابْنُ ثَابِتٍ - قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ يَزِيدَ، يُحَدِّثُ عَنْ زَيْدِ بْنِ ثَابِتٍ، أَنَّ النَّبِيَّ صلى الله
 عليه وسلم خَرَجَ إِلَى أُحُدٍ فَرَجَعَ نَاسٌ مِمَّنْ كَانَ مَعَهُ فَكَانَ أَصْحَابُ النَّبِيِّ صلى الله عليه
 وسلم فِيهِمْ فِرْقَتَيْنِ قَالَ بَعْضُهُمْ نَقْتُلُهُمْ ‏.‏ وَقَالَ بَعْضُهُمْ لاَ ‏.‏ فَنَزَلَتْ ‏{‏ فَمَا لَكُمْ فِي الْمُنَافِقِينَ
 فِئَتَيْنِ‏}‏