The Messenger of Allah ﷺ said, "When the imam says, 'not of those who have earned Your anger, nor of those who have gone astray' [Fatihah 1:7], say 'Ameen.' Whoever's utterance coincides with that of the angels will have his past sins forgiven."
أن رسول الله ﷺ قال: إذا قال الإمام: {غير المغضوب عليهم ولا الضالين} فقولوا: آمين، فمن وافق قوله قول الملائكة غفر له ما تقدم من ذنبه.
Malik narrated it in al-Salah (49) from Sumayy, the freedman of Abu Bakr, from Abu Salih Samman, from Abu Hurairah, who related it.Bukhari narrated it in al-Tafsir (4475) and Muslim in al-Salah (71:409), both from the hadith of Malik through the same chain, with the same wording.