Sahih al-bukhari:1322 Chapter: What is said about funerals, and those whose last words were: La ilãha ilallãh (none has the right to be worshipped but Allah) Book 23, Hadith 79

Narrated Ash-Shaibani: Ash-Shu`bi said, “Somebody who passed along with your Prophet (p.b.u.h) by a grave that was
separate from the other graves informed me (saying), “The Prophet (ﷺ)
led us (in the prayer) and we aligned behind him.” We said, “O Abu `Amr! Who told you this
narration?” He replied, “Ibn `Abbas.”