حَدَّثَنَا أَحْمَدُ بْنُ صَالِحٍ، حَدَّثَنَا ابْنُ أَبِي فُدَيْكٍ، أَخْبَرَنِي عَمْرُو بْنُ عُثْمَانَ بْنِ هَانِئٍ، عَنِ الْقَاسِمِ، قَالَ دَخَلْتُ عَلَى عَائِشَةَ فَقُلْتُ يَا أُمَّهْ اكْشِفِي لِي عَنْ قَبْرِ النَّبِيِّ صلى الله عليه وسلم وَصَاحِبَيْهِ رضى الله عنهما فَكَشَفَتْ لِي عَنْ ثَلاَثَةِ قُبُورٍ لاَ مُشْرِفَةٍ وَلاَ لاَطِئَةٍ مَبْطُوحَةٍ بِبَطْحَاءِ الْعَرْصَةِ الْحَمْرَاءِ قَالَ أَبُو عَلِيٍّ يُقَالُ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم مُقَدَّمٌ وَأَبُو بَكْرٍ عِنْدَ رَأْسِهِ وَعُمَرُ عِنْدَ رِجْلَىْ رَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏

Narrated Al-Qasim ibn Muhammad ibn AbuBakr: I said to Aisha! Mother, show me the grave of the Messenger of Allah (PBUH) and his two Companions (Allah be pleased with them). She showed me three graves which were neither high nor low, but were spread with soft red pebbles in an open space. Abu 'Ali said: It is said that the Messenger of Allah (PBUH) is forward, Abu Bakr is near his hed and 'Umar is near is feet. His head is at the feet of the Messenger of Allah (PBUH). Translation Not Available

Book Ref: Sunan Abi Dawud Book 21 Hadith 3220
Web Ref:  Sunan Abi Dawud Book 20 Hadith 3214