(1)
Abu Hurairah (RAA) narrated that the Messenger of Allah (ﷺ) said:
"If you offer the funeral prayer for a deceased person, supplicate Allah sincerely for him." Related by Abu Dawud.
Reference: Bulugh al-Maram 567
In-book reference: Book 3, Hadith 35
English translation: Book 3, Hadith 591