Al-Qasim bin Muhammad narrates: I went to Sayyidah Aishah (may Allah be pleased with her) and said: O mother, uncover for me the grave of the Messenger of Allah (peace and blessings be upon him) and his two companions. So she uncovered for me three graves, neither raised high nor flat against the ground, spread with the red gravel of the open courtyard. I saw the Messenger of Allah (peace and blessings be upon him) at the front, and Abu Bakr (may Allah be pleased with him) with his head between the shoulders of the Messenger of Allah (peace and blessings be upon him), and Umar (may Allah be pleased with him) with his head at the feet of the Messenger of Allah (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6758