It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The muezzin is forgiven to the extent of his adhan, and every dry and moist thing that heard his voice will bear witness for him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2027