At Siffin Imam Ali (a) gave the following instructions to his soldiers before the battle.
Do not take the initiative in fighting, let them begin it. It is because by the Favour of Allah you are on the side of truth and justice. Leave them until they begin their hostilities and then you are at liberty to take to fighting. Their keenness to begin a battle will be another proof of your sincere belief in the orders of Allah .
If Allah favours you with success and inflicts defeat to the enemy, then do not attack those who have surrendered, do not injure the disabled and weak, do not assault the wounded, do not excite women and do not make them angry with rude behaviour even if they use harsh and insulting words against your commander and officers because they are physically and mentally weak and get excited easily and frightened quickly. During the days of the Holy Prophet (peace of Allah be upon him and his descendants) we had strict orders not to touch, molest or insult women though they were unbelievers. Even in pre-Islamic days it was the custom that if a man struck a woman even with a stick or a stone, the revenge had to be taken by his sons and descendants.