Sahih Bukhari Volume 8, Book 74, Hadith Number 278.

Narated By Abu Said : The people of (the tribe of) Quraiza agreed upon to accept the verdict of Sa’d. The Prophet sent for him (Sa’d) and he came. The Prophet said (to those people), “Get up for your chief or the best among you!” Sa’d sat beside the Prophet and the Prophet said (to him), “These people have agreed to accept your verdict.” Sa’d said, “So I give my judgment that their warriors should be killed and their women and children should be taken as captives.” The Prophet said, “You have judged according to the King’s (Allah’s) judgment.” (See Hadith No. 447, Vol. 5)