Musnad Ahmad 1:38

Ya'qub ibn Ibrahim narrated to us, my father narrated to us, from Ibn Ishaq, who said: And Husayn ibn Abdullah narrated to me, from Ikrimah, the freed slave of Ibn Abbas, from Ibn Abbas, who said: When they wanted to dig for the Messenger of Allah, may Allah bless him and grant him peace, Abu Ubaydah ibn al-Jarrah used to make a *darih* (a trench in the middle of the grave) like the digging of the people of Makkah, and Abu Talhah Zayd ibn Sahl used to dig for the people of Madinah, and he used to make a *lahd* (a niche in the side of the grave). Al-Abbas summoned two men and said to one of them: "Go to Abu Ubaydah," and to the other: "Go to Abu Talhah. O Allah, choose for Your Messenger." He said: So the companion of Abu Talhah found Abu Talhah and brought him, and he made a *lahd* for the Messenger of Allah, may Allah bless him and grant him peace.