Excerpt from The Life of St. Antony:

But if any one having in mind the history of Job should say, 'Why then hath the devil gone forth and accomplished all things against him; and stripped him of all his possessions, and slew his children, and smote him with evil ulcers?' Let such a one, on the other hand, recognise that the devil was not the strong man, but God who delivered Job to him to be tried. Certainly he had no power to do anything, but he asked, and having received it, he hath wrought what he did. So also from this the enemy is the more to be condemned, for although willing he could not prevail against one just man. For if he could have, he would not have asked permission. But having asked not once but also a second time, he shows his weakness and want of power. And it is no wonder if he could do nothing against Job, when destruction would not have come even on his cattle had not God allowed it. And he has not the power over swine, for as it is written in the Gospel, they besought the Lord, saying, "Let us enter the swine." But if they had power not even against swine, much less have they any over men formed in the image of God.