[14].Surah Ibrahim {A.S} [Abraham (PBUH)]: Ayat 33-34

Ayat 33. And He has made the sun and the moon, both constantly pursuing their courses, to be of service to you; and He has made the night and the day, to be of service to you. Ayat 34. And He gave you of all that you asked for, and if you count the Blessings of Allah, never will you be able to count them. Verily! Man is indeed an extreme wrong-doer, - a disbeliever (an extreme ingrate, denies Allah's Blessings by disbelief, and by worshipping others besides Allah, and by disobeying Allah and His Prophet Muhammad  [SAWW](PBUH). 

Hazrat Ibn `Umar (May Allah be pleased with them) reported: Messenger of Allah  [SAWW](PBUH) said, "One who withdraws his hand from obedience (to the Amir) will find no argument (in his defense) when he stands before Allah on the Day of Resurrection; and one who dies without having sworn allegiance will die the death of one belonging to the Days of Ignorance.'' [Muslim Book 20, Chapter 13, Hadith # 4562].

Another narration is: The Messenger of Allah  [SAWW](PBUH) said, "He who dies having defected from obedience (to the Amir) and discards his association with the main body of the (Muslim) community, dies the death of one belonging to the Days of Jahiliyyah.''

Lesson : as mentioned above in Surah Ibrahim {A.S} Ayat 34. "denies Allah's Blessings by disbelief, and by worshipping others besides Allah," The Hadith makes it clear that it is binding upon Muslims to show obedience to the just Muslim ruler and to join forces with the Muslim Community to give allegiance to him as long as he does not call to a sin.