Prayer (Kitab Al-Salat)
2/179. Chapter:
Saying 'Amin Behind The Imam
Sunan Abi Dawud
حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، أَخْبَرَنَا سُفْيَانُ، عَنْ سَلَمَةَ، عَنْ حُجْرٍ أَبِي الْعَنْبَسِ الْحَضْرَمِيِّ، عَنْ وَائِلِ بْنِ حُجْرٍ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا قَرَأَ { وَلاَ الضَّالِّينَ } قَالَ " آمِينَ " . وَرَفَعَ بِهَا صَوْتَهُ .
Narrated Wa'il ibn Hujr: When the Messenger of Allah (ﷺ) recited the verse "Nor of those who go astray" (Surah al-Fatihah, verse 7), he would say Amin; and raised his voice (while uttering this word).
Reference : Sunan Abi Dawud 932In-book reference : Book 2, Hadith 543English translation : Book 3, Hadith 932