In some of the days of Siffin Amir al-mu'minin said to his followers about ways of fighting
O' crowd of Muslims! Make fear of Allah the routine of your life. Cover yourselves with peace of mind and clinch your teeth because this makes the sword slip off from the skull. Complete your armour and shake your swords in their sheathes before showing them out.
Have your eyes on the enemy. Use your spears on both sides and strike (the enemy) with swords. Keep in mind that you are before Allah and in the company of the Prophet's cousin. Repeat your attacks and feel ashamed of running away, because it is a shame for posterity and (cause of awarding you) fire on the Day of Judgement. Give your lives (to Allah) willingly and walk towards death with ease.
Beware of this great majority, and the pitched tent and aim at its centre because Satan is hiding in its cornet. He has extended his hand for assault and has kept back his foot for running away. Keep one enduring till the light of Truth dawns upon you.
While ye have the upper hand, and Allah is with you, and never will He depreciate your deeds. (Qur'an, 47:35)