It was narrated from Abu Hurairah, who heard it from the mouth of the Messenger of Allah (ﷺ):
"The Mu'adhdhin will be forgiven as far as his voice reaches, and every wet and dry thing will bear witness for him." (ID)
English reference (ID): Vol. 1, Book 7, Hadith 646 (ID)
Arabic reference (ID): Book 7, Hadith 652 (ID)