Bukhari Collection :: Book Number 9
9.227
Narrated Nafi`:When the people of Medina dethroned Yazid bin Muawiya, Ibn `Umar gathered his special friends and children and said, "I heard the Prophet saying, 'A flag will be fixed for every betrayer on the Day of Resurrection,' and we have given the oath of allegiance to this person (Yazid) in accordance with the conditions enjoined by Allah and His Apostle and I do not know of anything more faithless than fighting a person who has been given the oath of allegiance in accordance with the conditions enjoined by Allah and His Apostle , and if ever I learn that any person among you has agreed to dethrone Yazid, by giving the oath of allegiance (to somebody else) then there will be separation between him and me."