Ayesha reported,

Saad was wounded on the day of the Trench. A man from Quraysh named Hibban bin Araqa shot him, striking him in the median vein of his arm. The Prophet ﷺ pitched a tent for him in the mosque so he could visit him close by.When the Messenger of Allah ﷺ returned from the Trench, he laid down his weapons and bathed. Then Jibreel came to him, shaking the dust from his head, and said, "Have you laid down your weapons? By Allah, I have not laid mine down. Go out to them."The Prophet ﷺ asked, "Where to?"Jibreel pointed toward Banu Qurayza. The Messenger of Allah ﷺ went to them, and they agreed to come down on his judgment. He referred the judgment to Saad, who said, "I rule concerning them that the fighting men be killed, the women and children taken captive, and their property divided."Hisham said, my father told me, on the authority of Ayesha, that Saad had said, "O Allah, You know there is no people I would rather wage jihad against for Your sake than a people who denied Your Messenger ﷺ and drove him out. O Allah, I think You have ended the war between us and them. If anything remains of the war with Quraysh, keep me alive for it so I may wage jihad against them for Your sake. But if You have ended the war, then let this wound burst open and let my death be in it."His wound burst open at his throat. There was a tent in the mosque belonging to Banu Ghifar, and the first thing that startled them was blood flowing toward them. They called out, "People of the tent, what is this coming to us from your direction?"It was Saad's wound gushing with blood, and he died from it .

عن عائشة قالت

أصيب سعد يوم الخندق، رماه رجل من قريش، يقال له حبان بن العرقة، رماه في الأكحل، فضرب النبي ﷺ خيمة في المسجد ليعوده من قريب، فلما رجع رسول الله ﷺ من الخندق وضع السلاح واغتسل، فأتاه جبريل عليه السلام وهو ينفض رأسه من الغبار، فقال: وضعت السلاح، والله ما وضعته، اخرج إليهم. قال النبي ﷺ: فأين. فأشار إلى بني قريظة، فأتاهم رسول الله ﷺ فنزلوا على حكمه، فرد الحكم إلى سعد، قال: فإني أحكم فيهم: أن تقتل المقاتلة، وأن تسبى النساء والذرية، وأن تقسم أموالهم. قال هشام: فأخبرني أبي، عن عائشة: أن سعدا قال: اللهم إنك تعلم أنه ليس أحد أحب إلي أن أجاهدهم فيك، من قوم كذبوا رسولك ﷺ وأخرجوه، اللهم فإني أظن أنك قد وضعت الحرب بيننا وبينهم، فإن كان بقي من حرب قريش شيء فأبقني له، حتى أجاهدهم فيك، وإن كنت وضعت الحرب فافجرها واجعل موتي فيها، فانفجرت من لبته، فلم يرعهم، وفي المسجد خيمة من بني غفار، إلا الدم يسيل إليهم، فقالوا: يا أهل الخيمة، ما هذا الذي يأتينا من قبلكم؟ فإذا سعد يغذو جرحه دما، فمات رضي الله عنه.