Sahih Bukhari Volume 005, Book 057, Hadith Number 066.
Narated By 'Abdullah bin Az-Zubair : During the battle of Al-Ahzab, I and 'Umar bin Abi-Salama were kept behind with the women. Behold! I saw (my father) Az-Zubair riding his horse, going to and coming from Bani Quraiza twice or thrice. So when I came back I said, "O my father! I saw you going to and coming from Bani Quraiza?" He said, "Did you really see me, O my son?" I said, "Yes." He said, "Allah's Apostle said, 'Who will go to Bani Quraiza and bring me their news?' So I went, and when I came back, Allah's Apostle mentioned for me both his parents saying, "Let my father and mother be sacrificed for you.'"