Musnad Ahmad 1138:0

It was narrated to us by Abu al-Mughirah, who said: It was narrated to us by Safwan, who said: It was narrated to us by Shurayh ibn Ubayd, from Abu Umamah al-Harithi, that he said: I heard the Messenger of Allah (ﷺ) say: "Do not be like the people of the Book, who differed and split up after the clear proofs had come to them, so they perished." He said: "And do not be like the people of the Book, for they took their rabbis and their monks as lords besides Allah."