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
bukhari:6551 – Muʿādh b. Asad > al-Faḍl b. Mūsá > al-Fuḍayl > Abū Ḥāzim > Abū Hurayrah

The Prophet ﷺ said, "The width between the two shoulders of a Kafir (disbeliever) will be equal to the distance covered by a fast rider in three days."  

البخاري:٦٥٥١ – حَدَّثَنَا مُعَاذُ بْنُ أَسَدٍ أَخْبَرَنَا الْفَضْلُ بْنُ مُوسَى أَخْبَرَنَا الْفُضَيْلُ عَنْ أَبِي حَازِمٍ عَنْ أَبِي هُرَيْرَةَ

عَنِ النَّبِيِّ ﷺ قَالَ مَا بَيْنَ مَنْكِبَىِ الْكَافِرِ مَسِيرَةُ ثَلاَثَةِ أَيَّامٍ لِلرَّاكِبِ الْمُسْرِعِ  

See similar narrations below:

Collected by Muslim, Suyūṭī
muslim:2852 – Abū Kurayb And ʾAḥmad b. ʿUmar al-Wakīʿī > Ibn Fuḍayl from his father > Abū Ḥāzim > Abū Hurayrah Yarfaʿuh

The distance of the two shoulders of the non-believer in Hell will be a three-day journey for a swift rider.  

مسلم:٢٨٥٢ – حَدَّثَنَا أَبُو كُرَيْبٍ وَأَحْمَدُ بْنُ عُمَرَ الْوَكِيعِيُّ قَالاَ حَدَّثَنَا ابْنُ فُضَيْلٍ عَنْ أَبِيهِ عَنْ أَبِي حَازِمٍ عَنْ أَبِي هُرَيْرَةَ يَرْفَعُهُ قَالَ

مَا بَيْنَ مَنْكِبَىِ الْكَافِرِ فِي النَّارِ مَسِيرَةُ ثَلاَثَةِ أَيَّامٍ لِلرَّاكِبِ الْمُسْرِعِ وَلَمْ يَذْكُرِ الْوَكِيعِيُّ فِي النَّارِ