(36) باب مَا يَقُولُ إِذَا سَمِعَ الْمُؤَذِّنَ
Abu Sa'id al-Khudri reported the Messenger of Allah (May peace be upon him) as saying :
When you hear the Adhan, you should repeat the same words as the mu'adhdhin pronounces.
Reference: Sunan Abi Dawud 522
In-book reference: Book 2, Hadith 132
English translation: Book 2, Hadith 522