Sahih Bukhari Volume 9, Book 89, Hadith Number 257.

Narrated By Ibn ‘Abbas : The Prophet said, “If somebody sees his Muslim ruler doing something he disapproves of, he should be patient, for whoever becomes separate from the Muslim group even for a span and then dies, he will die as those who died in the Pre-lslamic period of ignorance (as rebellious sinners). (See Hadith No. 176 and 177)