Musannaf Ibn Abi Shayba 27:362

Abu Usama narrated to us, he said: Kahmas narrated to me, he said: Abdullah ibn Shaqiq narrated to me, he said: Al-Aqra’ narrated to me—Kahmas doubted, "I do not know if it is Al-Aqra’ the Mu’adhdhin or someone else"—he said: Umar sent for the Bishop. He said: So he was asking him while I was standing over them, shading them from the sun. He said: "Do you find me in your Book?" He said: "Your description and your deeds." He said: "How do you find me?" He said: "I find you as a horn of iron." Umar struck his face and said: "A horn of iron?" He said: "A severe commander." It was as if he was pleased with that. He said: "What do you find after me?" He said: "A truthful successor who favors his relatives." Umar said: "May Allah have mercy on Ibn Affan." He said: "What do you find after him?" He said: "A crack of iron." Umar had something in his hand that he was turning over, so he threw it away and said: "Oh, the calamity!" two or three times. He said: "Do not say that, O Commander of the Faithful, for he is a Muslim successor or a righteous man, but he will be succeeded while the sword is drawn and blood is being shed." He said: Then he turned to me and said: "The prayer."