If one jurist exercising independent legal reasoning were to believe that illicit sexual intercourse constituted transgression—as Allah Most High called it transgression in His words:

“Whoever seeks anything beyond that—it is they who are the transgressors.”

[Surah al-Muʾminūn: 7]

—and consequently killed an insane person for it, until it became clear to him that this was one of Allah’s prescribed penalties and could not be carried out (1) until the prohibition was known, whereas the insane person did not know that it was prohibited, no one would vilify him for this except someone who had vilified another for something even graver.

If someone were to argue:

“Fighting Muslims constitutes punishment of them, and they may not be punished until they know what is obligatory and what is prohibited. Yet Muʿāwiya’s supporters [whom ʿAlī fought (2)] (3) did not know that they were guilty of any sin. It was therefore not permissible for ʿAlī to fight them over something they did not know to be a sin. Even if they were sinful, the most that could be said (4) is that they failed to render the obligatory obedience. Yet many—if not most—of them did not know that they were required to obey and follow ʿAlī. Rather, they had doubts and interpretations that prevented them from knowing that this was obligatory. How, then, could it be permissible to fight someone who did not know that he had neglected an obligation or committed a prohibited act, even though his life was inviolable?”

Such an argument would not impugn ʿAlī’s imamate. How, then, could it impugn ʿUmar’s imamate?!

This is especially so because fighting over the neglect of an obligation is prescribed only when the harm caused by fighting is less than the harm caused by neglecting that obligation, and when the benefit achieved through fighting is greater than the benefit of refraining from it.