‏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....

‏البر والصلة والآداب‏ : Hadeeth No:6239 'A'isha reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: A believer does not undergo (the trouble) of running a thorn or more than that when Allaah effaces his sins....