Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said that when Banu Qurayzah made Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him) their arbiter, the Prophet (peace and blessings be upon him) sent for him, and he came riding a donkey. When he came near the mosque, he (peace and blessings be upon him) said: "Stand up for your chief, or for the best of you." He (peace and blessings be upon him) said: "These people have made you their arbiter." He said: "I judge concerning them that those capable of fighting be killed and the children be taken captive." So the Messenger of Allah (peace and blessings be upon him) said: "You have judged with the judgment of the King (Allah)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18017