I heard the Prophet ﷺ recite "nor of those who are astray" [Fatihah 1:7], and then he said "Ameen," prolonging his voice with it.
حدثنا وكيع حدثنا سفيان عن سلمة بن كهيل عن حجر بن عنبس
سمعت النبي ﷺ قرأ {ولا الضالين} فقال آمين يمد بها صوته
Its isnad is sahih. Hajr bin Anbas is trustworthy, one of the senior successors, and the hadith is like the one before it.