Musnad Ahmad 8:12

Abu Salamah al-Khuza'i narrated to us, Abdullah ibn Ja'far informed us, from Isma'il ibn Muhammad, from 'Amir ibn Sa'd, from Sa'd, who said: "Make a *lahd* (niche) for me, and set the bricks upright over me, just as was done for the Messenger of Allah, may Allah bless him and grant him peace."