Sahih Bukhari Volume 001, Book 003, Hadith Number 092.
Narated By Abu Musa : The Prophet was asked about things which he did not like, but when the questioners insisted, the Prophet got angry. He then said to the people, "Ask me anything you like." A man asked, "Who is my father?" The Prophet replied, "Your father is Hudhafa." Then another man got up and said, "Who is my father, O Allah's Apostle ?" He replied, "Your father is Salim, Maula (the freed slave) of Shaiba." So when 'Umar saw that (the anger) on the face of the Prophet he said, "O Allah's Apostle! We repent to Allah (Our offending you)."