Musnad Ahmad 1013:16

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Abu Hazim, from Sahl ibn Sa'd: Mount Uhud shook while the Prophet, peace and blessings of Allah be upon him, Abu Bakr, 'Umar, and 'Uthman were upon it. The Prophet, peace and blessings of Allah be upon him, said: "Be firm, O Uhud, for there is upon you nothing but a Prophet, a Truthful One (Siddiq), and two martyrs."