Musnad Ahmad 31:53

I heard Sufyan say: "And indeed, Allah, the Almighty and Majestic, will make you successors in it, so He will observe how you act. Beware, for every treacherous person shall have a banner on the Day of Resurrection at his posterior, according to the extent of his treachery." It was read to Sufyan: I heard Ali ibn Zayd, from Abu Nadra, from Abu Sa'id al-Khudri, from the Prophet, may Allah bless him and grant him peace.