Sahih Bukhari Volume 001, Book 003, Hadith Number 093.
Narated By Anas bin Malik : One day Allah's Apostle came out (before the people) and 'Abdullah bin Hudhafa stood up and asked (him) "Who is my father?" The Prophet replied, "Your father is Hudhafa." The Prophet told them repeatedly (in anger) to ask him anything they liked. 'Umar knelt down before the Prophet and said thrice, "We accept Allah as (our) Lord and Islam as (our) religion and Muhammad as (our) Prophet." After that the Prophet became silent.