(7) باب مَا يَقُولُ إِذَا سَمِعَ الْمُنَادِي
Narrated Abu Sa`id Al-Khudri:
Allah's Messenger (ﷺ) said, "Whenever you hear the Adhan, say what the Mu'adh-dhin is saying.
Reference: Sahih al-Bukhari 611
In-book reference: Book 10, Hadith 9
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 11, Hadith 585