Bismillah ar-rahman ar-rahim
'Aishah رضي الله عنها narrated : Sa'd رضي الله عنه was wounded on the day of Khandaq (i.e., Trench) when a man from Quraish, called Ibn Al-'Ariqah, hit him (with an arrow). He shot an arrow at Sa'd medial arm vein.
The Messenger of Allah صلى الله عليه وسلم pitched a tent for Sa'd in the mosque to keep him nearby. When the Prophet صلى الله عليه وسلم returned from the (battle) of Khandaq (i.e., Trench) and laid down his arms and took a bath, Jibril (Gabriel) عليه السلام came to him while he was shaking the dust off his head, and said, "You have laid down the arms? By Allah, I have no laid them down. Go towards them (to attack them)."
The Messenger of Allah صلى الله عليه وسلم said, "Where?"
Jibril pointed towards Banu Quraizah.
So the Messenger of Allah صلى الله عليه وسلم went to Banu Quraizah (and besieged them).
They then surrendered to the Prophet's judgement but he directed them to Sa'd to give his verdict on them.
Sa'd said, "I give my judgement that their warriors be killed, their woman and children be taken as captives, and their properties be distributed."
In another narration, the Messenger of Allah صلى الله عليه وسلم said to Sa'd : "You have passed on them to judgement of Allah, the Glorified," or he said : " You have judged by the Judgement of the King." (Bukhari : 4122 and Muslim : 1768)