The people of Qurayza agreed to surrender on the condition that Saad bin Muaz would decide their fate. The Messenger of Allah ﷺ sent for Saad, and he came riding on a donkey. When he drew near the mosque, the Messenger of Allah ﷺ said, "Stand for your leader," or he said, "for the best among you."Then he said, "These people have surrendered to your judgment."Saad said, "Their fighters shall be killed and their women and children taken captive."The Prophet ﷺ said, "You have judged with the judgment of Allah." And sometimes he said, "You have judged with the judgment of the King."
حدثنا محمد حدثنا شعبة عن سعد بن إبراهيم عن أبي أمامة بن سهل قال سمعت
نزل أهل قريظة على حكم سعد بن معاذ قال فأرسل رسول الله ﷺ إلى سعد فأتاه على حمار قال فلما دنا قريبا من المسجد قال رسول الله ﷺ قوموا إلى سيدكم أو خيركم ثم قال إن هؤلاء نزلوا على حكمك قال تقتل مقاتلتهم وتسبى ذراريهم قال فقال النبي ﷺ لقد قضيت بحكم الله وربما قال قضيت بحكم الملك
Its isnad is sahih. Saad bin Ibrahim bin Abdul-Rahman bin Awf Zuhri is a trustworthy imam, and Abu Umama bin Sahl, whose name is Asad bin Sahl, is also trustworthy and had seen the Prophet, some counted him among the companions. The hadith is found in Bukhari 4/1, in the chapter on jihad, when the enemy submits to the judgment of a man, and in Muslim 3/1389, number 1768, in the chapter on jihad, on the permissibility of fighting one who breaks a covenant.