It was incumbent to obey Imam 'Ali (as)

To prove the religious dimension, we have the hadith of Rasulullah (s):

"Whoever obeys ''Ali, obeys me, whoever obeys me, obeys Allah, whoever disobeys ''Ali, disobeys me, whoever disobeys me, disobeys Allah" [Kanz ul Ummal, hadith numbers 32973]

This hadith is absolutely explicit, obedience to Hadhrath ''Ali (as) is unconditional, it is on par with obedience to Rasulullah (s) and Allah (swt). Hence any disobedience to him, IS RELIGIOUS because it is deemed disobedience to Allah (swt).

Rasulullah (s) said:

"''Ali is with the Qur''an and the Qur''an is with ''Ali, the two shall not separate until they meet me at the Fountain of Kauthar" [Kanz ul Ummal hadith number 32912]. "''Ali is with the Truth and the Truth is with ''Ali" [Kanz ul Ummal hadith number 33018].

These two ahadith make it clear that every decision that Imam Ali (as) takes is Haqq and is supported by the Holy Qur''an and hence will ALWAYS be a religious decision. In other words if he declares war on Mu''awiya, it is the truth supported by the Qur''an, not influenced by political decision making.

If these hadith are not sufficient then we also have this clear hadith of Rasulullah (s) who said to his companions:

"Verily among you will be one who will fight for the meaning of the Qur''an in the same way that I fought for its revelation. People asked will that be Abu Bakr or Umar? Rasulullah (s) replied ''No, but he who is mending my shoes, that person was ''Ali" [Kanz ul Ummal hadith number 32967].

This hadith is absolutely explicit every Jihad of Hardhat ''Ali (as)''s is in defence of the Qur''an, to protect it from misinterpretation.

Adapted from the book: "Historic Background of Shiism"