Musnad Ahmad 30:2880

Aswad ibn Amir narrated to us, Abu Bakr narrated to us, from Abu Husayn, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "Follow the right course, and draw near [to perfection], and know that not one of you will be saved by his deeds." They said: "Not even you, O Messenger of Allah?" He said: "Not even me, unless Allah covers me with His mercy."