Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When the Imam recites « غَيْرِ الْمَغْضُوبِ عَلَيْهِمْ وَلَا الضَّالِّينَ », you should say Ameen. Indeed, the angels also say Ameen and the Imam also says Ameen. So, whoever's Ameen coincides with the Ameen of the angels, his previous sins are forgiven." This is the narration of San‘ani.