Qu'ran 3:151 "We will cast terror into the hearts of those who disbelieve for what they have associated with Allah of which He had not sent down [any] authority. And their refuge will be the Fire, and wretched is the residence of the wrongdoers."
Qu'ran 8:12 "[Remember] when your Lord inspired to the angels, "I am with you, so strengthen those who have believed. I will cast terror into the hearts of those who disbelieved, so strike [them] upon the necks and strike from them every fingertip."
Qu'ran 47:4 "So when you meet those who disbelieve, strike [their] necks until, when you have inflicted slaughter upon them, then secure their bonds, and either [confer] favor afterwards or ransom [them] until the war lays down its burdens. That [is the command]. And if Allah had willed, He could have taken vengeance upon them [Himself], but [He ordered armed struggle] to test some of you by means of others. And those who are killed in the cause of Allah - never will He waste their deeds."