Abu Dawud Book 2, Hadith Number 515.

Narated By AbuHurayrah : The Prophet (PBUH) said: The mu’adhdhin will receive forgiveness to the extent to which his voice reaches, and every moist and dry place will testify on his behalf; and he who attends (the congregation of) prayer will have twenty-five prayers recorded for him and will have expiation for sins committed between every two times of prayer.