Sahih Bukhari Volume 5, Book 59, Hadith Number 443.

Narrated By ‘Aisha : When the Prophet returned from Al-Khandaq (i.e. Trench) and laid down his arms and took a bath, Gabriel came and said (to the Prophet), You have laid down your arms? By Allah, we angels have not laid them down yet. So set out for them.” The Prophet said, “Where to go?” Gabriel said, “Towards this side,” pointing towards Banu Quraiza. So the Prophet went out towards them.