Musannaf Ibn Abi Shayba 27:377

Waki’ narrated to us, from Harun ibn Abi Ibrahim, from ‘Abdullah ibn ‘Ubayd ibn ‘Umayr, who said: Ibn ‘Abbas entered upon ‘Umar when he had been stabbed. He said to him, "O Commander of the Faithful, if your Islam was a victory, and if your leadership was a conquest, by Allah, you have filled the earth with justice, to the point that two men would dispute and then conclude at your command." ‘Umar said, "Seat me up." So they seated him up. He said, "Repeat your words to me." He repeated them to him. He said, "Will you testify to this statement for me before Allah on the day you meet Him?" He said, "Yes." ‘Umar was pleased by that and rejoiced.