It is narrated from Sayyiduna Wa'il bin Hujr (may Allah be pleased with him) that he prayed with the Prophet (peace and blessings be upon him), and when he (peace and blessings be upon him) said: "Not of those who have earned [Your] anger, nor of those who are astray", he said "Amin", and lowered his voice with it.
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18223