وَعَنْهُ قَالَ: «كَانَ رَسُولُ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: إِذَا فَرَغَ مِنْ قِرَاءَةِ أُمِّ اَلْقُرْآنِ رَفَعَ صَوْتَهُ وَقَالَ: «آمِينَ»
When the Messenger of Allah (radiyallahu anhu) completed the recitation of Surat Al-Fatiha, he raised his voice and said Amin. [Reported by ad-Daraqutni who graded it Hasan (good) and Al-Hakim who graded it Sahih (authentic)).
Bulugh al-Maram 345, Book 2, The Book of Prayer, Hadith 166. 1 min read