Musannaf Ibn Abi Shayba 37:464

Waki’ narrated to us, from Musa ibn Ubaydah, from Talhah ibn Ubayd Allah ibn Kurayz, who said: Umar said: "The thing I fear most for you is: greed that is obeyed, desires that are followed, and a man’s self-admiration for his own opinion; and it is the most severe of them."