Musnad Ahmad 30:2899

He said: Meaning Abd al-Rahman, Hammad narrated to us, from Muhammad ibn Ziyad, who said: I heard Abu Hurairah saying: I heard Abu al-Qasim, may Allah bless him and grant him peace, saying: "If you knew what I know, you would laugh little and weep much. But be upright, draw near [to the truth], and receive glad tidings."