Sunan Ibn Majah, Book 6, Hadith 1555 (In-Book) ⓘ
It was narrated from Abu Hurairah that the Prophet said: “Whoever has the funeral prayer offered for him by one hundred Muslims, he will be forgiven.”
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عُبَيْدُ اللَّهِ، أَنْبَأَنَا شَيْبَانُ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ ـ صلى الله عليه وسلم ـ قَالَ " مَنْ صَلَّى عَلَيْهِ مِائَةٌ مِنَ الْمُسْلِمِينَ غُفِرَ لَهُ " .
also referenced under: Hadith 1488 (Reference) & Volume 2, Book 6, Hadith 1488 (DarusSalam)