Musnad Abu Ya'la al-Mawsili 42:215

Zuhayr narrated to us, Abd al-Rahman ibn Mahdi narrated to us, from Shu'bah, from Sa'd ibn Ibrahim, who said: I heard Abu Umamah ibn Sahl narrating from Abu Sa'id al-Khudri that the Banu Qurayzah submitted to the judgment of Sa'd ibn Mu'adh. So, he (the Prophet) sent for Sa'd, and he came upon a donkey. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Stand up for the best of you," or "for your leader." He said: "These people have submitted to your judgment." He said: "Then I judge regarding them that their fighters be killed and their offspring be taken captive." The Messenger of Allah (peace and blessings of Allah be upon him) said: "You have judged with the judgment of Allah." And he said once: "You have judged with the judgment of the King."