Sahih Bukhari Volume 004, Book 054, Hadith Number 413.
Narated By 'Imran bin Husain : Some people of Bani Tamim came to the Prophet and he said (to them), "O Bani Tamim! rejoice with glad tidings." They said, "You have given us glad tidings, now give us something." On hearing that the color of his face changed then the people of Yemen came to him and he said, "O people of Yemen ! Accept the good tidings, as Bani Tamim has refused them." The Yemenites said, "We accept them. Then the Prophet started taking about the beginning of creation and about Allah's Throne. In the mean time a man came saying, "O 'Imran! Your she-camel has run away!'' (I got up and went away), but l wish I had not left that place (for I missed what Allah's Apostle had said).