Musnad Ahmad 31:496

Yahya ibn Adam narrated to us, Fudayl ibn Marzuq, the freed slave of Banu Anz, narrated to me, from Atiyyah al-Awfi, from Abu Sa’id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "No one will enter Paradise except by the mercy of Allah." We said: "O Messenger of Allah, not even you?" He said: "Not even me, unless Allah covers me with His mercy." And he gestured with his hand above his head.