Hadith 3:35
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.
وَعَنْهُ أَنَّ اَلنَّبِيَّ - صلى الله عليه وسلم -قَالَ: { إِذَا صَلَّيْتُمْ عَلَى اَلْمَيِّتِ فَأَخْلِصُوا لَهُ اَلدُّعَاءَ } رَوَاهُ أَبُو دَاوُدَ, وَصَحَّحَهُ ابْنُ حِبَّانَ
Original Reference: Bulugh al-Maram 567