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).
كَانَ رَسُولُ اللَّهِ ﷺ إِذَا قَرَأَ { وَلاَ الضَّالِّينَ } قَالَ آمِينَ وَرَفَعَ بِهَا صَوْتَهُ