"Indeed, amount the last (of orders) Allah's Messenger ordered me with was to employ a Mu'adh-dhin who would not take a wage for his Adhan."
Jami` at-Tirmidhi Book 2, Hadith 61
← Previous Hadith Allah's Messenger said: "Whenyou hear the call (to prayer) then say the similar to what the Mu'adh-dhin says"

Jami` at-Tirmidhi Book 2, Hadith 60 Next Hadith → Allah's Messenger said: "Whoever says, when he hears the Mu'adh-dhin: (Wa Ana Ashadu An La Ilaha Illallah, Wahdahu La Sharika Lahu, Wa Anna Muhammadan Abduhu Wa Rasuluhu, Radittu Billahi Rabban Wa Bil-Islam Dinan, Wa Bi Muhammadin Rasulan) 'I too testify that none has the right to be worshiped but Allah, Alone without partners, and that Muhammad is His slave and Messenger, I am pleased with Allah as my Lord, with Islam as my religion and Muhammad as a Messenger.' - Allah will pardon his sins for him."

Jami` at-Tirmidhi Book 2, Hadith 62