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."
Sahih al-Bukhari Book 23, Hadith 91
← Previous Hadith I offered the funeral prayer behind Ibn `Abbas and he recited Al-Fatiha and said, "You should know that it (i.e. recitation of Al-Fatiha) is the tradition of the Prophet (ﷺ) Muhammad.

Sahih al-Bukhari Book 23, Hadith 90 Next Hadith → A black person, a male or a female used to clean the Mosque and then died. The Prophet (p.b.u.h) did not know about it . One day the Prophet (ﷺ) remembered him and said, "What happened to that person?" The people replied, "O Allah's Messenger (ﷺ)! He died." He said, "Why did you not inform me?" They said, "His story was so and so (i.e. regarded him as insignificant)." He said, "Show me his grave." He then went to his grave and offered the funeral prayer.

Sahih al-Bukhari Book 23, Hadith 92