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). (Using translation from Abū Dāʾūd 932)
كَانَ رَسُولُ اللهِ ﷺ إِذَا قَالَ {وَلَا الضَّالِّينَ} قَالَ «آمِينَ» يَرْفَعُ بِهَا صَوْتَهُ