رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 1578
The Book of the Prohibited actions
Prohibition of Deriding one's Lineage
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : اثْنَتَانِ فِي النَّاسِ هُمَا بِهِمْ كُفْرٌ: الطَّعْنُ فِي النَّسَبِ، وَالنِّيَاحَةُ عَلَى الْمَيِّتِ ((رَوَاهُ مُسْلِم)).
Abu Hurairah (May Allah be pleased with him) said: The Messenger of Allah (ﷺ) said, "Two matters are signs of disbelief on the part of those who indulge in them: Defaming and speaking evil of a person's lineage, and wailing over the dead." [Muslim].
Riyad as-Salihin, 1578