Qu'ran 002:190

Fight in the cause of God those who fight you, but do not transgress limits; for God loveth not transgressors.

Qu'ran 002:191

And slay them wherever ye catch them, and turn them out from where they have Turned you out; for tumult and oppression are worse than slaughter; but fight them not at the Sacred Mosque, unless they (first) fight you there; but if they fight you, slay them. Such is the reward of those who suppress faith.

Qu'ran 002:192

But if they cease, God is Oft-forgiving, Most Merciful.

Qu'ran 5:53

… whoso kills a soul, unless it be for murder or for wreaking corruption in the land, it shall be as if he had killed all mankind; and he who saves a life, it shall be as if he had given life to all mankind.

But if the enemies incline towards peace, do you also incline towards peace. And trust in God! For He is the one who hears and knows all things.

Abu Bakr al-Siddiq, the first Caliph, gave these instructions to his armies:

I instruct you in ten matters: Do not kill women, children, the old, or the infirm; do not cut down fruit-bearing trees; do not destroy any town . . .

Since Jihad involves killing and shedding the blood of men, Allah indicated that these men are committing disbelief in Allah, associating with Him (in the worship) and hindering from His path, and this is a much greater evil and more disastrous than killing.