Musannaf Ibn Abi Shayba 36:296

Ghundar narrated to us, from Shu'bah, from Sa'd ibn Ibrahim, from Abu Umamah ibn Sahl, that he heard him saying: I heard Abu Sa'id al-Khudri saying: The people of Qurayzah surrendered to the judgment of Sa'd ibn Mu'adh. He said: So the Messenger of Allah (may Allah bless him and grant him peace) sent for Sa'd. He said: So he came to him on a donkey. He said: When he drew near to the mosque, the Messenger of Allah (may Allah bless him and grant him peace) said: "Stand up for your leader," or "your best one." Then he said: "Indeed, these people have surrendered to your judgment." He said: "You shall kill their fighters and take their offspring captive." He said: So the Messenger of Allah (may Allah bless him and grant him peace) said: "You have judged with a judgment," and sometimes he said: "You have judged with the judgment of Allah."