Musnad Ahmad 25:802

Husayn ibn Muhammad narrated to us, Jarir ibn Hazim narrated to us, from Muhammad—meaning Ibn Ishaq—from Husayn, from Ikrimah, from Ibn Abbas, who said: There were two men in Medina who used to dig graves: Abu Ubaydah ibn al-Jarrah, who used to dig for the people of Mecca, and Abu Talhah, who used to dig for the Ansar and make a *lahd* (a niche in the side of the grave) for them. He said: "When the Messenger of Allah (peace and blessings of Allah be upon him) passed away, al-Abbas sent two men to them and said: 'O Allah, choose for Your Prophet.' They found Abu Talhah, but they did not find Abu Ubaydah. So he dug for him and made a *lahd* for him."