Musannaf Ibn Abi Shayba 3:5586

Waki’ narrated to us, he said: Fitr narrated to us, he said: I heard ‘Ikrimah saying: I reached the people, and they had a clamor in their mosques with "Amin" when the Imam said: "Not of those who have evoked [Your] anger or of those who are astray."