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.
muslim:2403eḤasan b. ʿAlī al-Ḥulwānī And ʾAbū Bakr b. Isḥāq > Saʿīd b. Abū Maryam > Muḥammad b. Jaʿfar b. Abū Kathīr > Sharīk b. ʿAbdullāh b. Abū Namir > Saʿīd b. al-Musayyab > Abū Mūsá al-Ashʿarī

I concluded (from the manner of their sitting) the (order) of their graves. (The three) would be together (the graves of the Holy Prophet, Hadrat Abu Bakr and Hadrat Umar) and that of 'Uthman would be separate (from them).  

مسلم:٢٤٠٣eحَدَّثَنَا حَسَنُ بْنُ عَلِيٍّ الْحُلْوَانِيُّ وَأَبُو بَكْرِ بْنُ إِسْحَاقَ قَالاَ حَدَّثَنَا سَعِيدُ بْنُ أَبِي مَرْيَمَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرِ بْنِ أَبِي كَثِيرٍ أَخْبَرَنِي شَرِيكُ بْنُ عَبْدِ اللَّهِ بْنِ أَبِي نَمِرٍ عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ عَنْ أَبِي مُوسَى الأَشْعَرِيِّ قَالَ

خَرَجَ رَسُولُ اللَّهِ ﷺ يَوْمًا إِلَى حَائِطٍ بِالْمَدِينَةِ لِحَاجَتِهِ فَخَرَجْتُ فِي إِثْرِهِ وَاقْتَصَّ الْحَدِيثَ بِمَعْنَى حَدِيثِ سُلَيْمَانَ بْنِ بِلاَلٍ وَذَكَرَ فِي الْحَدِيثِ قَالَ ابْنُ الْمُسَيَّبِ فَتَأَوَّلْتُ ذَلِكَ قُبُورَهُمُ اجْتَمَعَتْ هَا هُنَا وَانْفَرَدَ عُثْمَانُ