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

ذِكْرُ الْإِخْبَارِ عَمَّا يَجْعَلُ اللَّهُ غِلَظَ جُلُودِ الْكَافِرِ فِي النَّارِ بِهِ

ibnhibban:7487 – Aḥmad b. ʿAlī b. al-Muthanná > Isḥāq b. Ibrāhīm b. Abū Isrāʾīl al-Marwazī > Ḥumayd b. ʿAbd al-Raḥman > al-Ḥasan b. Ṣāliḥ > Hārūn b. Saʿd > Abū Ḥāzim > Abū Hurayrah

The molar tooth of an unbeliever or the canine teeth of an unbeliever will be like Uhud and the thickness of his skin a three night's journey. (Using translation from Muslim 2851)  

ابن حبّان:٧٤٨٧ – أَخْبَرَنَا أَحْمَدُ بْنُ عَلِيِّ بْنِ الْمُثَنَّى قَالَ حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ بْنِ أَبِي إِسْرَائِيلَ الْمَرْوَزِيُّ قَالَ حَدَّثَنَا حُمَيْدُ بْنُ عَبْدِ الرَّحْمَنِ عَنِ الْحَسَنِ بْنِ صَالِحٍ عَنْ هَارُونَ بْنِ سَعْدٍ عَنْ أَبِي حَازِمٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ «ضِرْسُ الْكَافِرِ أَوْ نَابُ الْكَافِرِ مِثْلُ أُحُدٍ وَغِلَظُ جِلْدِهِ مَسِيرَةُ ثَلَاثٍ»  

See similar narrations below:

Collected by Muslim, Suyūṭī
muslim:2851 – Surayj b. Yūnus > Ḥumayd b. ʿAbd al-Raḥman > al-Ḥasan b. Ṣāliḥ > Hārūn b. Saʿd > Abū Ḥāzim > Abū Hurayrah

The molar tooth of an unbeliever or the canine teeth of an unbeliever will be like Uhud and the thickness of his skin a three night's journey.  

مسلم:٢٨٥١ – حَدَّثَنِي سُرَيْجُ بْنُ يُونُسَ حَدَّثَنَا حُمَيْدُ بْنُ عَبْدِ الرَّحْمَنِ عَنِ الْحَسَنِ بْنِ صَالِحٍ عَنْ هَارُونَ بْنِ سَعْدٍ عَنْ أَبِي حَازِمٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ ضِرْسُ الْكَافِرِ أَوْ نَابُ الْكَافِرِ مِثْلُ أُحُدٍ وَغِلَظُ جِلْدِهِ مَسِيرَةُ ثَلاَثٍ