Hazrat Abu Huraira narrates in a marfu’ form that when the reciter says Ameen, you should also say Ameen. Thus, whoever’s Ameen coincides with the Ameen of the angels, his previous sins will be forgiven.

Hazrat Abdul Jabbar bin Wa'il narrates from his father that I offered prayer in the company of the Holy Prophet (peace and blessings of Allah be upon him). When the Prophet (peace and blessings of Allah be upon him) said { غَیْرِ الْمَغْضُوبِ عَلَیْہِمْ، وَلاَ الضَّالِّینَ }, he (peace and blessings of Allah be upon him) said Ameen.

Hazrat Wa'il bin Hujr narrates that I heard the Holy Prophet (peace and blessings be upon him) recite { وَلاَ الضَّالِّینَ } and then say Ameen. In this, the Prophet (peace and blessings be upon him) prolonged his voice. And (Imam) Abu Hanifa's opinion has been mentioned that: the Imam will not raise his voice while saying Ameen, and the followers will say Ameen.