From Sahih Bukhari (Hadith 1326):
Narrated 'Amir:Ibn `Abbas (who was at that time a boy) said, "Allah's Messenger (ﷺ) came to a grave and the people said, 'He or she was buried yesterday.' " Ibn `Abbas added, "We aligned behind the Prophet (ﷺ) and he led the funeral prayer of the deceased
Reference: Bukhari 1326