The Book of the Adhan (The Call to Prayer)
7/33. Chapter:
Saying What The Mu'adhdhin Says
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنِ الزُّهْرِيِّ، عَنْ عَطَاءِ بْنِ يَزِيدَ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِذَا سَمِعْتُمُ النِّدَاءَ فَقُولُوا مِثْلَ مَا يَقُولُ الْمُؤَذِّنُ " .
It was narrated from Abu Sa'eed Al-Khudri that the Messenger of Allah (S.A.W) said: "When you hear the call, say what the Mu'adhdhin says."
Reference : Sunan an-Nasa'i 673In-book reference : Book 7, Hadith 48English translation : Vol. 1, Book 7, Hadith 674