34 Temptations, therefore, take place by means of Satan not by his power, but by the Lord's permission, either for the purpose of punishing men for their sins, or of proving and exercising them in accordance with the Lord's compassion. And there is a very great difference in the nature of the temptations into which each one may fall. For Judas, who sold his Lord, did not fall into one of the same nature as Peter fell into, when, under the influence of terror, he denied his Lord. There are also temptations common to man, I believe, when every one, though well disposed, yet yielding to human frailty, falls into error in some plan, or is irritated against a brother, in the earnest endeavour to bring him round to what is right, yet a little more than Christian calmness demands: concerning which temptations the apostle says, “There has no temptation taken you but such as is common to man;” while he says at the same time, “But God is faithful, who will not suffer you to be tempted above that you are able; but will with the temptation also make a way to escape, that you may be able to bear it.” And in that sentence he makes it sufficiently evident that we are not to pray that we may not be tempted, but that we may not be led into temptation. For we are led into temptation, if such temptations have happened to us as we are not able to bear. But when dangerous temptations, into which it is ruinous for us to be brought and led, arise either from prosperous or adverse temporal circumstances, no one is broken down by the irksomeness of adversity, who is not led captive by the delight of prosperity.
35. The seventh and last petition is, “But deliver us from evil.” For we are to pray not only that we may not be led into the evil from which we are free, which is asked in the sixth place; but that we may also be delivered from that into which we have been already led. And when this has been done, nothing will remain terrible, nor will any temptation at all have to be feared. And yet in this life, so long as we carry about our present mortality, into which we were led by the persuasion of the serpent, it is not to be hoped that this can be the case; but yet we are to hope that at some future time it will take place: and this is the hope which is not seen, of which the apostle, when speaking, said, “But hope which is seen is not hope.” But yet the wisdom which is granted in this life also, is not to be despaired of by the faithful servants of God. And it is this, that we should with the most wary vigilance shun what we have understood, from the Lord's revealing it, is to be shunned; and that we should with the most ardent love seek after what we have understood, from the Lord's revealing it, is to be sought after. For thus, after the remaining burden of this mortality has been laid down in the act of dying, there shall be perfected in every part of man at the fit time, the blessedness which has been begun in this life, and which we have from time to time strained every nerve to lay hold of and secure.
Source: Our Lord's Sermon on the Mount (New Advent)