Sahih al-Bukhari 1336
Narrated Sulaiman Ash-Shaibani:
I heard Ash-Shu`bi saying, "I was told by a man who had passed with the Prophet (p.b.u.h) by a grave 
that was separate from the other graves that he (the Prophet (ﷺ) ) led them in the prayer and they prayed 
behind him." I said, "O Abu `Amr! Who narrated that to you?" He replied, "Ibn `Abbas."
حَدَّثَنَا حَجَّاجُ بْنُ مِنْهَالٍ، حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنِي سُلَيْمَانُ الشَّيْبَانِيُّ، قَالَ سَمِعْتُ الشَّعْبِيَّ، قَالَ أَخْبَرَنِي مَنْ، مَرَّ مَعَ النَّبِيِّ صلى الله عليه وسلم عَلَى قَبْرٍ مَنْبُوذٍ فَأَمَّهُمْ وَصَلَّوْا خَلْفَهُ‏.‏ قُلْتُ مَنْ حَدَّثَكَ هَذَا يَا أَبَا عَمْرٍو قَالَ ابْنُ عَبَّاسٍ ـ رضى الله عنهما ـ‏.‏