Musnad Ahmad 30:2351

Muhammad ibn Ubayd narrated to us, he said: Al-A’mash narrated to us, from Abu Salih, from Abu Hurayrah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Imam is a guarantor, and the Mu'adhdhin is a trustee. O Allah, guide the Imams, and forgive the Mu'adhdhins." And likewise, Aswad narrated it to us, he said: Sharik narrated to us, from Al-A’mash, from Abu Salih, from Abu Hurayrah, just as Muhammad said: "Guide the Imams, and forgive the Mu'adhdhins." And likewise, Ibn Fudayl also said it, and Za'idah also narrated it to us from Mu'awiyah, meaning from him.