It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The muezzin is forgiven to the extent of his adhan, and every moist and dry thing that heard him bears witness for him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2028