When Imam Ali (a) sent an expedition of 3000 soldiers under Ma'qil bin Qays Riyahi against the Syrians, he issued the following instructions.
Fear Allah before Whom attendance is inevitable, and with other than Whom there is no meeting. Do not fight except with those who fight you. Travel in the two cool periods (i.e., morning and evening). Let the men have a midday sleep. March easily and do not travel during the early night for Allah has made it for resting and has ordained it for staying, nor for journeying. Therefore, give rest to your body in the night and let your carrier-beasts also rest. 
When you are sure that morning has appeared and when dawn has dawned, commence your journey with Allah's blessings. If and when you face the enemy stand in the midst of your comrades. Do not get too near the foe like one who wants to commence the fighting, nor remain too distant like one who is afraid of action, till you receive my orders. Hatred for them should not lead you to fight before inviting them (to guidance) and exhausting your pleas before them.