1 Peter 1:13

From the greatness and excellency of grace he draws an exhortation, that it surely behoved them the more readily to receive the grace of God, as the more bountifully he bestowed it upon them. And we must notice the connection: he had said, that so elevated was the kingdom of Christ, to which the gospel calls us, that even angels in heaven desire to see it; what then ought to be done by us who are in the world? Doubtless, as long as we live on earth, so great is the distance between us and Christ, that in vain he invites us to himself. It is hence necessary for us to put off the image of Adam and to cast aside the whole world and all hinderances, that being thus set at liberty we may rise upwards to Christ. And he exhorted those to whom he wrote, to be prepared and sober, and to hope for the graces offered to them, and also to renounce the world and their former life, and to be conformed to the will of God. (15)

Then the first part of the exhortation is, to gird up the loins of their mind and to direct their thoughts to the hope of the grace presented to them. In the second par, he prescribes the manner, that having their minds changed, they were to be formed after the image of God.

13Wherefore gird up the loins of your mind It is a similitude taken from an ancient custom; for when they had long garments, they could not make a journey, nor conveniently do any work, without being girded up. Hence these expressions, to gird up one’s-self for a work or an undertaking. He then bids them to remove all impediments, that being set at liberty they might go on to God. Those who philosophize more refinedly about the loins, as though he commanded lusts to be restrained and checked, depart from the real meaning of the Apostle, for these words mean the same with those of Christ,

“Let your loins be girded about, and burning lamps in your hands,”
(Luke 12:35,)

except that Peter doubles the metaphor by ascribing loins to the mind. And he intimates that our minds are held entangled by the passing cares of the world and by vain desires, so that they rise not upward to God. Whosoever, then, really wishes to have this hope, let him learn in the first place to disentangle himself from the world, and gird up his mind that it may not turn aside to vain affections. And for the same purpose he enjoins sobriety, which immediately follows; for he commends not temperance only in eating and drinking, but rather spiritual sobriety, when all our thoughts and affections are so kept as not to be inebriated with the allurements of this world. For since even the least taste of them stealthily draws us away from God, when one plunges himself into these, he must necessarily become sleepy and stupid, and he forgets God and the things of God.

Hope to the end, or, Perfectly hope. He intimates that those who let their minds loose on vanity, did not really and sincerely hope for the grace of God; for though they had some hope, yet as they vacillated and were tossed to and fro in the world, there was no solidity in their hope. Then he says, for the grace which will be brought to you, in order that they might be more prompt to receive it. God ought to be sought, though far off; but he comes of his own will to meet us. How great, then, must be our ingratitude if we neglect the grace that is thus set before us! This amplification, then, is especially intended to stimulate our hope.

What he adds, At the revelation of Jesus Christ, may be explained in two ways: that the doctrine of the Gospel reveals Christ to us; and that, as we see him as yet only through a mirror and enigmatically, a full revelation is deferred to the last day. The first meaning is approved by Erasmus, nor do I reject it. The second seems, however, to be more suitable to the passage. For the object of Peter was to call us away beyond the world; for this purpose the fittest thing was the recollection of Christ’s coming. For when we direct our eyes to this event, this world becomes crucified to us, and we to the world. Besides, according to this meaning, Peter used the expression shortly before. Nor is it a new thing for the apostles to employ the preposition ἐν in the sense of εἰς. Thus, then, I explain the passage, — “You have no need to make a long journey that you may attain the grace of God; for God anticipates you; inasmuch as he brings it to you.” But as the fruition of it will not be until Christ appears from heaven, in whom is hid the salvation of the godly, there is need, in the meantime, of hope; for the grace of Christ is now offered to us in vain, except we patiently wait until the coming of Christ.