Luke 22:32

But I have prayed for thee,.... Christ prayed for all the apostles; but particularly for Peter, because he was in the greatest danger: whether the prayer Christ refers to was that in John 17:1 in which are many passages relating to the preservation, sanctification, final perseverance and glorification of the apostles, as well as of other saints, as in John 17:9 and so these words might be spoken a little after that prayer was ended, which was about this same time; or whether it was any other, and only mental, and not vocal, is not certain: however, the petition was,

that thy faith fail not; Satan in his temptations strikes principally at the faith of God's people; that being a grace which gives much glory to God, and in the exercise of which believers have much peace, joy, and comfort; both which he envies and grudges; and it is also a shield which keeps off, and quenches his fiery darts, and is a piece of armour he is sadly harassed with, and therefore endeavours all he can to weaken and destroy it, or wrest it out of their hands: but though, through the power of sin, and the force of temptation, it may fail as to some degree of the steadfastness of it, as to the acting and exercise of it, and as to the sense believers may have of it; yet never as to its principle, it being an irrevocable gift of God's grace; a work of his almighty power; a solid and substantial grace, even the substance of things hoped for; an immortal and incorruptible seed, and of which Christ is the author and finisher; and to nothing more is its security owing, than to the prayers of Christ, which are always heard, and to his powerful mediation, and prevalent intercession; Christ is the advocate of his people; he prays that they might have faith, and then he prays, that it may not fail; and it shall not, notwithstanding all the opposition of hell, and earth, unto it:

and when thou art converted, strengthen thy brethren: Peter was now a converted man, and had been for some years; but whereas he would fall by temptation into a very great sin of denying his Lord, and which was attended with such circumstances as made him look like an unconverted, and an unregenerate man; his recovery by the fresh exercise of faith in Christ, and repentance for his sins, is called conversion: and which was not his own act, but owing to the power and efficacy of divine grace; see Jeremiah 31:18. Some versions render it in the imperative, "in time, convert, turn, or return, and strengthen thy brethren"; as the Syriac, Arabic, and Persic versions: as he afterwards did: for whereas all the disciples forsook Christ, and fled, some one way, and some another, Peter, after his recovery, got them together again, and returned with them to Jerusalem; when they with him assembled together, till the third day Christ was risen: he strengthened their faith in the Messiah, and put them upon filling up the place of Judas, by choosing another apostle; and on the day of "Pentecost" preached a most excellent sermon, which as it was made useful for the conversion of three thousand sinners, was, doubtless, a means of confirming the minds of the disciples; and he has left two exceeding useful epistles for the strengthening of his brethren in all ages of time; the design of which is to establish the saints in faith and holiness, that they may not be drawn aside, and fall from the steadfastness of their faith, either by the lusts of the flesh, or by the persecutions of men, or by the error of the wicked.