Not graded
Bulugh al-Maram 283
وَعَنْهُ قَالَ : { كَانَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -إِذَا فَرَغَ مِنْ قِرَاءَةِ أُمِّ اَلْقُرْآنِ رَفَعَ صَوْتَهُ وَقَالَ :
"آمِينَ"
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)).
Cited in Bulugh al-Maram (No. 283).