Hadith 6:835
Sharik narrated to us, from Jabir, from Abu Ja'far, Salim, and al-Qasim, who said: The grave of the Prophet (may Allah bless him and grant him peace), Abu Bakr, and Umar was a mound facing the Qibla. Bricks were set up for them, and a *lahd* (niche) was dug for them.
حدثنا شريك عن جابر عن أبي جعفر وسالم والقاسم قالوا كان قبر النبي صلى الله عليه وسلم وأبي بكر وعمر جثا قبلة نصب لهم اللبن نصبا ولحد لهم لحدا