Sahih al-Bukhari 4122

On the day of Al-Khandaq (battle of the Trench' the medial arm vein of Sa`d bin Mu`ad [??] was injured and the Prophet (ﷺ) pitched a tent in the mosque to look after him. There was another tent for Banu Ghaffar in the mosque and the blood started flowing from Sa`d's tent to the tent of Bani Ghaffar. They shouted, "O occupants of the tent! What is coming from you to us?" They found that Sa`d' wound was bleeding profusely and Sa`d died in his tent.

Sa'd was wounded on the day of the Battle of the Ditch. A man from the Quraish called Ibn al-Ariqah shot at him an arrow which pierced the artery in the middle of his forearm. The Messenger of Allah (ﷺ) pitched a tent for him in the mosque and would inquire after him being in close proximity. When he returned from the Ditch and laid down his arms and took a bath, the angel Gabriel appeared to him and he was removing dust from his hair (as if he had just returned from the battle). The latter said: You have laid down arms. By God, we haven't (yet) laid them down. So march against them. The Messenger of Allah (ﷺ) asked: Where? He pointed to Banu Quraiza. So the Messenger of Allah (ﷺ) fought against them. They surrendered at the command of the Messenger of Allah (ﷺ), but he referred the decision about them to Sa'd who said: I decide about them that those of them who can fight be killed, their women and children taken prisoners and their properties distributed (among the Muslims).

"On the day of (the battle of) Al-Ahzab, Sa'd bin Mu'adh was struck by an arrow such that the upper vein or lower vein of his forearm was severed. So the Messenger of Allah (ﷺ) tried to stop it with fire, but it made his arm bleed profusely so he left it. Then he did it another time but it caused it to bleed profusely. Upon seeing that he said: 'O Allah! Do not allow my soul depart until my eyes are comforted by elimination of Banu Quraizah.' He pressed his vein closed and it did not bleed a drop before they surrendered to the arbitration of Sa'd bin Mu'adh. He (the Prophet (ﷺ)) sent to him (Sa'd) who judged that their men should be killed, their women should be spared, and that the Muslims may share them among themselves. With this, the Messenger of Allah (ﷺ) said: 'You have judged according to Allah's judgement for them.' And they were four hundred. Then when he finished killing them, his vein opened up and he died." [He said:] There are narrations on this topic from Abu Sa'eed and 'Atiyyah Al-Qurazi. [Abu 'Eisa said:] This Hadith is Hasan Sahih.

"Sa'd was wounded on the day of Al-Khandaq [1] when a man of Quraish shot him in the medial arm vein. The Messenger of Allah (ﷺ) pitched a tent (Khaimah) for him in the Masjid so that he could visit him close at hand." [1] Al-Khandaq means the trench. This indicates the battle of the trench which took place during the fifth year after Hijrah.