Do not fight them unless they initiate the fighting, because, by the grace of Allāh, you are in the right and to leave them till they begin fighting will be another point from your side against them. If, by the will of Allāh, the enemy is defeated then do not kill the runner away, do not strike a helpless person, do not finish off the wounded, and do not inflict pain on women even though they may attack your honour with filthy words and abuse your officers, because they are weak in character, mind and intelligence. We have been ordered to desist from them although they may be unbelievers. Even in pre-Islamic (al-jāhiliyyah) period if a man struck a woman with a stone or a stick he was rebuked along with his posteriors after him.
 The responsibility for the war and fighting that took place between Amīr al-mu’minīn and Mu‘āwiyah lies solely on Mu‘āwiyah because he brought about the war by laying the wrong blame for ‘Uthmān’s blood on Amīr al-mu’minīn, although the real facts about the causes of ‘Uthmān’s killing and by whom he was killed were not unknown to him. But since there was no way for him to achieve his end save by creating an occasion for war, he entered into war to retain his authority which was evidently offensive and which cannot by any means be considered as permissible, because revolt and rebellion against the rightful Imām is unlawful according to the general consensus of Muslims. Thus, Abū Zakariyyā Yaḥyā ibn Sharaf an-Nawāwī (631/1233 -676/1277) writes:
Do not fight against those in authority in matters of governance, nor raise objections against them except when you observe them committing things which you know are definitely against Islam. If you see them doing such things regard it bad for them and speak the truth wherever you may be, but rising against them or fighting is prohibited by the consensus of Muslims. (Sharḥ Ṣaḥīḥ Muslim, vol. 2, p. 125. In agreement with this view, see also, al-Qāḍī Abū Bakr Muḥammad ibn aṭ-Ṭayyib al-Bāqillānī [338/950 — 403/1013], the Ash‘arite great scholar, in at-Tamhīd, p. 186; and Sa‘du’d-Dīn Mas‘ūd ibn ‘Umar at-Taftāzānī [712/1312 -793/1390] in Sharḥ al-Maqāṣid, vol. 2, p. 272)
Muḥammad ibn ‘Abd al-Karīm ash-Shahrastānī writes :
Whoever rises against the true Imām, by the unanimity of opinion of the (Muslim) community, is known as a Khārijite, the deviator. The same is the case of rising, during the days of the companions, against the rightful Imams, or even after them against those who followed them in virtue. (al-Milal wa’n-niḥal, vol. l, p. 114)
There is no doubt that Mu‘āwiyah’s action was the result of uprising and revolt, and to take up arms for the purpose of stopping the advance of the one who revolts is not to be regarded as being against any code of peacefulness or peace-loving. Rather, it is a natural right of the oppressed; and if he is deprived of this right then there will remain no way of preventing oppression and tyranny or of safeguarding rights in the world. That is why Allāh has permitted taking up arms against rebels. Thus, Allāh says :
And if two parties of the believers fall into a quarrel (among themselves), restore ye peace between them two; but if one of the two transgresseth against the other, (then) fight ye (all against) that which transgresseth until it complieth with the command of Allāh; and if it complieth then restore ye peace between the two with justice, and act ye justly; Verily, Allāh loveth the just ones. (Qur’ān, 49:9)
It was the first plea to which Amīr al-mu’minīn pointed out by saying, “By the Grace of Allāh you are in the right,” but even after exhaustion of this plea he prevented his army from taking the initiative in fighting, because he wished that the initiative should not be from his side and that he should take up the sword only in defence. Consequently, when all his effort for peace and tranquility proved futile and the enemy took the step towards war, this was the second argument in their favour, after which Amīr al-mu’minīn could not be blamed for getting ready to fight, nor accused of aggressive action. It was rather an obligation to stop oppression and tyranny that he had to discharge and which Allāh has permitted in plain words. Thus, Allāh’s command is that :
And fight in the cause of Allāh (against) those who fight you but be not aggressive; for verily Allāh loveth not the aggressors. (Qu’ān, 2:190)
Besides, fighting against Amīr al-mu’minīn means fighting against the Prophet, as the Prophet’s saying: “O’ ‘Alī, your peace is my peace and your war is my war” (Ibn al-Maghāzilī, al-Manāqib, p. 5; Ibn Abi’l-Ḥadīd, vol. 18, p. 24). In this way whatever punishment should be for fighting against the Prophet should be for fighting against Amīr al-mu’minīn. For him who wages war against the Prophet, Allāh has laid down the following punishment.
To recompense of those who war against Allāh and His Apostle, and strive in the land, spreading mischief (therein), is only that they be slain or crucified or their hands and their feet should be cut off, from the opposite sides, or be banished from the land; This for them shall be the disgrace in this world, and for them, in the hereafter, shall be a great torment. (Qur’ān, 5:33)
Apart from this, the instructions that Amīr al-mu’minīn issued in connection with the war, namely that no runner away or wounded should be molested, are so high from the moral point of view that they can be regarded as a sublime specimen of moral values and the high standard of Islamic fighting. Then, these instructions were not confined to mere words but Amīr al-mu’minīn followed them to the letter, and ordered others also to follow them strictly. He did not, on any occasion, tolerate the chasing of a runner away, attack the helpless or molest women, in fact, on the battlefield of Jamal, where the command of the opposite force was with a woman, he did not change his principle. After the defeat and vanquishment of the foe he gave proof of his high character and sent ‘Ā’ishah to Medina under guard. Had there been someone other than Amīr al-mu’minīn he would have proposed the same punishment as that which ought to be awarded for such a step! Thus, Ibn Abi’l-Ḥadīd has written:
What she did with Amīr al-mu’minīn, if she had done the same with (Caliph) ‘Umar and had spread rebellion against him among the people, he would , after securing victory over her, have killed her and cut her into pieces, but Amīr al-mu’minīn was very fore-bearing and largehearted. (Sharḥ Nahj al-balāghah, vol. 17, p. 254)