Musnad Ahmad 30:1881

Bahz narrated to us, Hammad narrated to us, from Muhammad—meaning Ibn Ziyad—from Abu Hurairah, who said: I heard Abu al-Qasim (may Allah bless him and grant him peace) say: "By the One in Whose hand is my soul, there is not one among you whom his deeds will cause to enter Paradise." They said: "Not even you, O Messenger of Allah?" He said: "Not even me, unless Allah covers me with mercy and grace from Him," and he placed his hand upon his head.