‏الإمارة : Hadeeth No:4568 It has been narrated on the authority of Aba Sa'id al-Khudri that the Messenger of Allaah (sallAllaahu alayhi wa sallam) said: When oath of allegiance has been taken for two caliphs, kill the one for whom the oath was taken later....

‏البيوع : Hadeeth No:3609 Abu Huraira (Allaah be pletsed with him) reported like this from Allaah's Messenger (sallAllaahu alayhi wa sallam)....