كتاب الجهاد والسير
32  
The Book of Jihad and Expeditions
(37)
Chapter: The Battle of Uhud
(37)
باب غَزْوَةِ أُحُدٍ ‏‏
Sahih Muslim 1792 a

It has been narrated on the authority of 'Abdullah who said:

It appeared to me as if I saw the Messenger of Allah (ﷺ) (and heard him) relate the story of a Prophet who had been beaten by his people, was wiping the blood from his face and was saying. My Lord, forgive my people, for they do not know.
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا الأَعْمَشُ، عَنْ شَقِيقٍ، عَنْ عَبْدِ اللَّهِ، قَالَ كَأَنِّي أَنْظُرُ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم يَحْكِي نَبِيًّا مِنَ الأَنْبِيَاءِ ضَرَبَهُ قَوْمُهُ وَهُوَ يَمْسَحُ الدَّمَ عَنْ وَجْهِهِ وَيَقُولُ ‏ "‏ رَبِّ اغْفِرْ لِقَوْمِي فَإِنَّهُمْ لاَ يَعْلَمُونَ ‏"‏ ‏.‏
Reference : Sahih Muslim 1792a
In-book reference : Book 32, Hadith 128
USC-MSA web (English) reference : Book 19, Hadith 4418
  (deprecated numbering scheme)