question #1 Sahih al-Bukhari 1326, Book 23, Hadith 82 : What is the significance of performing a funeral prayer in Islam?

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.”