Sahih Bukhari Volume 008, Book 077, Hadith Number 617.
Narated By Al-Bara' bin 'Azib : I saw the Prophet on the Day of (the battle of) Al-Khandaq, carrying earth with us and saying, "By Allah, without Allah we would not have been guided, neither would we have fasted, nor would we have prayed. O Allah! Send down Sakina (calmness) upon us and make our feet firm when we meet (the enemy). The pagans have rebelled against us, but if they want to put us in affliction (i.e., fight us) we refuse (to flee)." (See Hadith No. 430, Vol. 5).