Lest they should be wearied with the Second Epistle as though the first was sufficient, he says that it was not written in vain, because they stood in need of being often stirred up. To make this more evident, he shews that they could not be beyond danger, except they were well fortified, because they would have to contend with desperate men, who would not only corrupt the purity of the faith, by false opinions, but do what they could to subvert entirely the whole faith. By saying, I stir up your pure mind, he means the same as though he had said, "I wish to awaken you to a sincerity of mind." And the words ought to be thus explained, "I stir up your mind that it may be pure and bright." For the meaning is, that the minds of the godly become dim, and as it were contract rust, when admonitions cease. But we also hence learn, that men even endued with learning, become, in a manner, drowsy, except they are stirred up by constant warnings. [1] It now appears what is the use of admonitions, and how necessary they are; for the sloth of the flesh smothers the truth once received, and renders it inefficient, except the goads of warnings come to its aid. It is not then enough, that men should be taught to know what they ought to be, but there is need of godly teachers, to do this second part, deeply to impress the truth on the memory of their hearers. And as men are, by nature, for the most part, fond of novelty and thus inclined to be fastidious, it is useful for us to bear in mind what Peter says, so that we may not only willingly suffer ourselves to be admonished by others, but that every one may also exercise himself in calling to mind continually the truth, so that our minds may become resplendent with the pure and clear knowledge of it.

Footnotes

1 - The Apostle evidently admits that they had a sincere or a pure mind, that is, freed from the pollutions referred to in the last chapter; but still they stood in need of being stirred up by admonitions: hence their minds were not, in a strict sense, perfect, though sincere. -- Ed.

This second epistle, beloved, I now write unto you - This expression proves that he had written a former epistle, and that it was addressed to the same persons as this. Compare Introduction, Section 3.
In both which I stir up your pure minds - That is, the main object of both epistles is the same - to call to your remembrance important truths which you have before heard, but which you are in danger of forgetting, or from which you are in danger of being turned away by prevailing errors. Compare the notes at 2-Peter 1:12-15. The word rendered "pure" (εἰλικρινής eilikrinēs) occurs only here and in Philippians 1:10, where it is rendered "sincere." The word properly refers to "that which may be judged of in sunshine;" then it means "clear, manifest;" and then "sincere, pure" - as that in which there is no obscurity. The idea here perhaps is, that their minds were open, frank, candid, sincere, rather than that they were "pure." The apostle regarded them as "disposed" to see the truth, and yet as liable to be led astray by the plausible errors of others. Such minds need to have truths often brought fresh to their remembrance, though they are truths with which they had before been familiar.

This second epistle - In order to guard them against the seductions of false teachers, he calls to their remembrance the doctrine of the ancient prophets, and the commands or instructions of the apostles, all founded on the same basis.
He possibly refers to the prophecies of Enoch, as mentioned by Jude, Jde 1:14, Jde 1:15; of David, Psalm 1:1, etc.; and of Daniel, Daniel 12:2, relative to the coming of our Lord to judgment: and he brings in the instructions of the apostles of Christ, by which they were directed how to prepare to meet their God.

This (1) second epistle, beloved, I now write unto you; in [both] which I stir up your pure minds by way of remembrance:
(1) The remedy against those wicked enemies, both of true doctrine and holiness, is to be sought for by the continual meditation of the writings of the prophets and apostles.

This second epistle, beloved, I now write unto you,.... This is a transition to another part of the epistle; for the apostle having largely described false teachers, the secret enemies of the Christian religion under a profession of it, passes on to take notice of the more open adversaries and profane scoffers of it; and from their ridicule of the doctrine of Christ's second coming, he proceeds to treat of that, and of the destruction of the world, and the future happiness of the saints: he calls this epistle his "second epistle", because he had written another before to the same persons; and that the author of this epistle was an apostle, is evident from 2-Peter 3:2; and which, compared with 2-Peter 1:18 shows him to be the Apostle Peter, whose name it bears, and who was an eyewitness to the transfiguration of Christ on the mount, Matthew 17:1, he addresses these saints here, as also in 2-Peter 3:8, under the character of "beloved"; because they were the beloved of God, being chosen by him according to his foreknowledge, and regenerated by him, according to his abundant mercy; and were openly his people, and had obtained mercy from him, and like precious faith with the apostles; and were also the beloved of Christ, being redeemed by him, not with gold and silver, but with his precious blood; for whom he suffered, and who were partakers of his sufferings, and the benefits arising from them, and who had all things given them by him, pertaining to life and godliness, and exceeding great and precious promises; and were likewise beloved by the apostle, though strangers, and not merely as Jews, or because they were his countrymen, but because they were the elect of God, the redeemed of Christ, and who were sanctified by the Spirit, and had the same kind of faith he himself had. The Syriac and Arabic versions read, "my beloved"; and the Ethiopic version, "my brethren": his end in writing both this and the former epistle follows;
in both which I stir up your pure minds by way of remembrance; that this was his view both in this and the former epistle, appears from 1-Peter 1:13; he calls their minds pure; not that they were so naturally, for the minds and consciences of men are universally defiled with sin; nor are the minds of all men pure who seem to be so in their own eyes, or appear so to others; nor can any man, by his own power or works, make himself pure from sin; only the blood of Christ purges and cleanses from it; and a pure mind is a mind sprinkled with that blood, and which receives the truth as it is in Jesus, in the power and purity of it, and that holds the mystery of the faith in a pure conscience. Some versions, as the Vulgate Latin and Arabic, render the word "sincere", as it is in Philippians 1:10; and may design the sincerity of their hearts in the worship of God, in the doctrines of Christ, and to one another, and of the grace of the Spirit of God in them; as that their faith was unfeigned, their hope without hypocrisy, and their love without dissimulation, and their repentance real and genuine; but yet they needed to be stirred up by way of remembrance, both of the truth of the Gospel, and the duties of religion; for saints are apt to be forgetful of the word, both of its doctrines and its exhortations; and it is the business of the ministers of the word to put them in mind of them, either by preaching or by writing; and which shows the necessity and usefulness of the standing ministry of the Gospel: the particulars he put them in mind of next follow.

The purified minds of Christians are to be stirred up, that they may be active and lively in the work of holiness. There will be scoffers in the last days, under the gospel, men who make light of sin, and mock at salvation by Jesus Christ. One very principal article of our faith refers to what only has a promise to rest upon, and scoffers will attack it till our Lord is come. They will not believe that he will come. Because they see no changes, therefore they fear not God, Psalm 55:19. What he never has done, they fancy he never can do, or never will do.

SURENESS OF CHRIST'S COMING, AND ITS ACCOMPANIMENTS, DECLARED IN OPPOSITION TO SCOFFERS ABOUT TO ARISE. GOD'S LONG SUFFERING A MOTIVE TO REPENTANCE, AS PAUL'S EPISTLES SET FORTH; CONCLUDING EXHORTATION TO GROWTH IN THE KNOWLEDGE OF CHRIST. (2Pe. 3:1-18)
now--"This now a second Epistle I write." Therefore he had lately written the former Epistle. The seven Catholic Epistles were written by James, John, and Jude, shortly before their deaths; previously, while having the prospect of being still for some time alive, they felt it less necessary to write [BENGEL].
unto you--The Second Epistle, though more general in its address, yet included especially the same persons as the First Epistle was particularly addressed to.
pure--literally, "pure when examined by sunlight"; "sincere." Adulterated with no error. Opposite to "having the understanding darkened." ALFORD explains, The mind, will, and affection, in relation to the outer world, being turned to God [the Sun of the soul], and not obscured by fleshly and selfish regards.
by way of--Greek, "in," "in putting you in remembrance" (2-Peter 1:12-13). Ye already know (2-Peter 3:3); it is only needed that I remind you (Jde 1:5).

This second epistle. This language implies a former letter written to the same persons to whom this is addressed.
I stir up your pure minds. In both letters his object was mainly to exhort them to holy lives.
By way of remembrance. By reminding you of the claims of Christ as shown by prophets and apostles.
That ye be mindful of the words. Both of what was spoken by the prophets in the Old Testament, and of what the apostles have now spoken.
Us the apostles. The Twelve, and Paul, who is alluded to in 2-Peter 3:15.
Knowing this first. The apostles and prophets have reminded them that there will be scoffers in the last days. Under the last dispensation.
Where is the promise of his coming? This question is asked by the scoffers, as though the coming of Christ was so long delayed that all hope had ended. They take advantage of the disappointment to try to destroy faith.
All things continue. The scoffers assert that the regular order of nature continues right on as it was from the beginning. They forget the deluge.