Musnad Ahmad 30:925

Hassan ibn Musa narrated to us, Zuhayr narrated to us, Sa’d ibn ‘Ubayd al-Ta’i narrated to us—I said to Zuhayr: "Is he Abu al-Mujahid?" He said: "Yes"—Abu al-Mudillah, the freed slave of the Mother of the Believers, narrated to me that he heard Abu Hurayrah. We said: "O Messenger of Allah," and he mentioned the hadith.