Urwah bin al-Zubayr narrates: On the day of the Battle of the Trench, Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him) was struck by an arrow which cut the vein of his arm called "al-akhal". People say that Hibban bin Qays shot him, who belonged to Banu al-Ariqah, a branch of Banu Amir bin Lu'ayy; others say that Abu Usamah al-Jushami shot him. Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him) said: "O my Lord! Grant me healing (of my heart) regarding Banu Qurayzah before I die." Then his wound, after it had burst open, stopped (that is, the blood stopped flowing from it). The narrator says: The Prophet (peace and blessings be upon him) kept Banu Qurayzah under siege until they asked him to appoint someone as arbiter between himself and them, whose arbitration they would accept. The Prophet (peace and blessings be upon him) said: "Choose whomever you wish from my Companions; his word will be heard." So they chose Sayyiduna Sa'd bin Mu'adh, and the Prophet (peace and blessings be upon him) was pleased with him, and they also accepted this. The Prophet (peace and blessings be upon him) ordered that their weapons be placed in a house, and by the order of the Prophet those people were tied up and kept in the house of Sayyiduna Usamah bin Zayd (may Allah be pleased with him). Then the Prophet (peace and blessings be upon him) sent for Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him). He came riding on the donkey of a Bedouin; people say that the cloth spread on that donkey was stuffed with leaves. A man from Banu Abd al-Ashhal was coming along with him. As he walked with him, he was extolling the right of Banu Qurayzah, mentioning their alliance and mentioning the conduct those people had shown on the day of Bu'ath, (saying) that those people had chosen you over everyone else, hoping that you would show kindness and be gentle with them, so take care of this, for in those people there is both beauty and numbers for you. That man said a great deal about this, but Sayyiduna Sa'd (may Allah be pleased with him) gave him no reply. When they came near, that man said to Sayyiduna Sa'd (may Allah be pleased with him): "Why do you not give me any reply?" Sayyiduna Sa'd (may Allah be pleased with him) said: "By Allah! Concerning Allah Almighty, I will not care about the blame of any blamer." So that man parted from him and went to his people, having despaired of getting those people spared, and he told his people what he had said to Sayyiduna Sa'd (may Allah be pleased with him) and what Sayyiduna Sa'd (may Allah be pleased with him) had replied to him. Then Sayyiduna Sa'd (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) said: "O Sa'd! Give judgement between us and them!" Sayyiduna Sa'd (may Allah be pleased with him) said: "I give this judgement concerning them: that their fighting men be killed, their captives be divided, their wealth be taken, and their children and women be taken captive." The Prophet (peace and blessings be upon him) said: "Sa'd has judged concerning them according to the judgement of Allah." Some people state that they had submitted to the judgement of the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) handed over the responsibility of judging concerning them to Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him). Then those people were brought out group after group and their necks were struck. When Huyayy bin Akhtab was brought, the Prophet (peace and blessings be upon him) said: "Has Allah Almighty disgraced you?" He said: "You have prevailed over me, and I do not blame myself concerning you." By the order of the Prophet (peace and blessings be upon him) he was taken to Ahjar al-Zayt, which is in the market, and there his neck was struck. All of this took place before the eyes of Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him). People also say that the wound of Sayyiduna Sa'd (may Allah be pleased with him) had healed and he was close to recovering, but then he made this supplication: "O Allah! O Lord of the heavens and the earth! No people are more hateful to me than the people who denied Your Messenger and forced him to leave. I think that You have lifted the war from between us and them. If war still remains between us and them, then keep me alive so that I may fight those people in Your path; and if You have lifted the war from between us and them, then let this place begin to flow (with blood) and let my death be through this wound." So Allah Almighty made his wound flow, and he slept through the night, and the people did not even realise until he passed away; his wound kept flowing until he died. (Allamah al-Haythami says:) I say: Part of it is narrated in the Sahih from Sayyidah Aishah (may Allah be pleased with her) with a connected chain.
Al-Tabarani recorded it as a mursal narration; its chain contains Ibn Lahi'ah, whose hadith is hasan (fair) but has weakness in it.