بُلُوغُ الْمَرَامِ
Bulugh al-Maram 283
The Book of Prayer
وَعَنْهُ قَالَ : { كَانَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -إِذَا فَرَغَ مِنْ قِرَاءَةِ أُمِّ اَلْقُرْآنِ رَفَعَ صَوْتَهُ وَقَالَ : آمِينَ . } رَوَاهُ اَلدَّارَقُطْنِيُّ وَحَسَّنَهُ , وَالْحَاكِمُ وَصَحَّحَهُ . [1] .
Narrated [Abu Hurairah (RA)]: When Allah's Messenger (RA) 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)).
Sunnah.com reference: Book 2, Hadith 169