Sahih Bukhari Volume 003, Book 044, Hadith Number 664.
Narated By Salama : Once the journey food diminished and the people were reduced to poverty. They went to the Prophet and asked his permission to slaughter their camels, and he agreed. 'Umar met them and they told him about it, and he said, "How would you survive after slaughtering your camels?" Then he went to the Prophet and said, "O Allah's Apostle! How would they survive after slaughtering their camels?" Allah's Apostle ordered 'Umar, "Call upon the people to bring what has remained of their food." A leather sheet was spread and al I the journey food was collected and heaped over it. Allah's Apostle stood up and invoked Allah to bless it, and then directed all the people to come with their utensils, and they started taking from it till all of them got what was sufficient for them. Allah's Apostle then said, "I testify that None has the right to be worshipped but Allah, and I am His Apostle."