It was narrated from Sulaiman Ash-Shaibani from Ash-Sha'bi:

"Some people passed by an isolated grave with the Messenger of Allah and he led them in prayer and they formed rows behind him." I said: "Who was that O Abu 'Amr?" He said: "Ibn 'Abbas."

أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ شُعْبَةَ، عَنْ سُلَيْمَانَ الشَّيْبَانِيِّ، عَنِ الشَّعْبِيِّ، : أَخْبَرَنِي مَنْ، مَرَّ مَعَ رَسُولِ اللَّهِ ﷺ عَلَى قَبْرٍ مُنْتَبِذٍ، فَأَمَّهُمْ وَصَفَّ خَلْفَهُ، قُلْتُ : مَنْ هُوَ يَا أَبَا عَمْرٍو قَالَ : ابْنُ عَبَّاسٍ .