I heard Ash-Shuʿbi saying, "A person who was accompanying the Prophet ﷺ passed by a grave that was separated from the other graves told me that the Prophet ﷺ once led the people in the (funeral) prayer and the people had aligned behind him. I said, "O Aba ʿAmr! Who told you about it?" He said, "Ibn ʿAbbas." (Using translation from Bukhārī 857)
أَخْبَرَنِي مَنْ مَرَّ مَعَ رَسُولِ اللهِ ﷺ عَلَى قَبْرٍ مَنْبُوذٍ فَأَمَّهُمْ وَصَفُّوا خَلْفَهُ فَقُلْتُ يَا أَبَا عَمْرٍو مَنْ حَدَّثَكَ؟ قَالَ ابْنُ عَبَّاسٍ