Musannaf Ibn Abi Shayba 33:1211

Khalaf ibn Khalifah narrated to us, from Asbagh al-Warraq, from Abu Nadrah, that Umar sent Haram ibn Hayyan to [oversee] the horses. He became angry at a man and ordered that his neck be struck. Then he turned to his companions and said, "May Allah not reward you with good; you did not advise me when I spoke, nor did you restrain me from my anger. By Allah, I will never again hold a position of authority for you." Then he wrote to Umar, "O Commander of the Faithful, I have no capacity for the subjects, so send for your position."