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
← Previous Hadith Allah's Messenger said: "The Imam is answerable and the Mu'adh-dhin is entrusted. O Allah! Guide the Imams and pardon the Mu'adh-dhins."

Jami` at-Tirmidhi Book 2, Hadith 59 Next Hadith → "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