Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
muslim:67 – [Chain 1] Abū Bakr b. Abū Shaybah > Abū Muʿāwiyah [Chain 2] Ibn Numayr > Abū And Muḥammad b. ʿUbayd > al-Aʿmash > Abū Ṣāliḥ > Abū Hurayrah

Two (things) are found among men which are tantamount to unbelief: slandering one's lineage and lamentation on the dead.  

مسلم:٦٧ – وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ حَدَّثَنَا أَبُو مُعَاوِيَةَ ح وَحَدَّثَنَا ابْنُ نُمَيْرٍ وَاللَّفْظُ لَهُ حَدَّثَنَا أَبِي وَمُحَمَّدُ بْنُ عُبَيْدٍ كُلُّهُمْ عَنِ الأَعْمَشِ عَنْ أَبِي صَالِحٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ اثْنَتَانِ فِي النَّاسِ هُمَا بِهِمْ كُفْرٌ الطَّعْنُ فِي النَّسَبِ وَالنِّيَاحَةُ عَلَى الْمَيِّتِ  

See similar narrations below:

Collected by Aḥmad, Suyūṭī
ahmad:9690 – Muḥammad b. ʿUbayd > al-Aʿmash > Abū Ṣāliḥ > Abū Hurayrah

[Machine] The Messenger of Allah ﷺ said, "There are two things among people that are considered as disbelief: mourning loudly for the deceased and insulting lineage."  

أحمد:٩٦٩٠ – حَدَّثَنَا مُحَمَّدُ بْنُ عُبَيْدٍ قَالَ حَدَّثَنَا الْأَعْمَشُ عَنْ أَبِي صَالِحٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللهِ ﷺ ثِنْتَانِ هُمَا بِالنَّاسِ كُفْرٌ نِيَاحَةٌ عَلَى الْمَيِّتِ وَطَعْنٌ فِي النَّسَبِ  

ahmad:10434 – Ibn Numayr > al-Aʿmash > Abū Ṣāliḥ > Abū Hurayrah

Two (things) are found among men which are tantamount to unbelief: slandering one's lineage and lamentation on the dead. (Using translation from Muslim 67)  

أحمد:١٠٤٣٤ – حَدَّثَنَا ابْنُ نُمَيْرٍ أَخْبَرَنَا الْأَعْمَشُ عَنْ أَبِي صَالِحٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللهِ ﷺ اثْنَتَانِ فِي النَّاسِ هُمَا بِهِمْ كُفْرٌ الطَّعْنُ فِي النَّسَبِ وَالنِّيَاحَةُ عَلَى الْمَيِّتِ  

suyuti:512a –

Two (things) are found among men which are tantamount to unbelief: slandering one's lineage and lamentation on the dead. (Using translation from Muslim 67)   

السيوطي:٥١٢a –

"اثنان في الناسِ هما بهم كُفْرٌ: الطعن في الأنساب، والنياحة على الميت".  

[حم] أحمد [م] مسلم عن أبى هريرة