Seeing then that all these things shall be dissolved - Since this is an undoubted truth.
What manner of persons ought ye to be in all holy conversation and godliness - In holy conduct and piety. That is, this fact ought to be allowed to exert a deep and abiding influence on us, to induce us to lead holy lives. We should feel that there is nothing permanent on the earth that this is not our abiding home; and that our great interests are in another world. We should be serious, humble, and prayerful; and should make it our great object to be prepared for the solemn scenes through which we are soon to pass. An habitual contemplation of the truth, that all that we see is soon to pass away, would produce a most salutary effect on the mind. It would make us serious. It would repress ambition. It would lead us not to desire to accumulate what must so soon be destroyed. It would prompt us to lay up our treasures in heaven. It would cause us to ask with deep earnestness whether we are prepared for these amazing scenes, should they suddenly burst upon us.

All these things shall be dissolved - They will all be separated, all decomposed; but none of them destroyed. And as they are the original matter out of which God formed the terraqueous globe, consequently they may enter again into the composition of a new system; and therefore the apostle says, 2-Peter 3:13 : we look for new heavens and a new earth - the others being decomposed, a new system is to be formed out of their materials. There is a wonderful philosophic propriety in the words of the apostle in describing this most awful event.
What manner of persons ought ye to be - Some put the note of interrogation at the end of this clause, and join the remaining part with the 12th verse, thus: Seeing then that all these things shall be dissolved, what manner of persons ought ye to be? By holy conversation and godliness, expecting and earnestly desiring the coming of the day of God, etc. Only those who walk in holiness, who live a godly and useful life, can contemplate this most awful time with joy.
The word σπευδοντας, which we translate hasting unto, should be tendered earnestly desiring, or wishing for; which is a frequent meaning of the word in the best Greek writers.

(11) [Seeing] then [that] all these things shall be dissolved, what manner [of persons] ought ye to be in [all] holy conversation and godliness,
(11) An exhortation to purity of life, setting before us that horrible judgment of God, both to bridle our wantonness, and also to comfort us, so that we are found watching and ready to meet him at his coming.

Seeing then that all these things shall be dissolved,.... By fire; the heaven with all its host, sun, moon, and stars, clouds, meteors, and fowls of the air; the earth, and all that is upon it, whether of nature, or art; and, since nothing is more certain than such a dissolution of all things,
what manner of persons ought ye to be in all holy conversation and godliness? not as the scoffers and profane sinners, who put away this evil day far from them, but as men, who have their loins girt, and their lights burning, waiting for their Lord's coming; being continually in the exercise of grace, and in the discharge of their religious duties, watching, praying, hearing, reading; living soberly, righteously, and godly; guarding against intemperance and worldly mindedness, and every worldly and hurtful lust.

From the doctrine of Christ's second coming, we are exhorted to purity and godliness. This is the effect of real knowledge. Very exact and universal holiness is enjoined, not resting in any low measure or degree. True Christians look for new heavens and a new earth; freed from the vanity to which things present are subject, and the sin they are polluted with. Those only who are clothed with the righteousness of Christ, and sanctified by the Holy Ghost, shall be admitted to dwell in this holy place. He is faithful, who has promised. Those, whose sins are pardoned, and their peace made with God, are the only safe and happy people; therefore follow after peace, and that with all men; follow after holiness as well as peace. Never expect to be found at that day of God in peace, if you are lazy and idle in this your day, in which we must finish the work given us to do. Only the diligent Christian will be the happy Christian in the day of the Lord. Our Lord will suddenly come to us, or shortly call us to him; and shall he find us idle? Learn to make a right use of the patience of our Lord, who as yet delays his coming. Proud, carnal, and corrupt men, seek to wrest some things into a seeming agreement with their wicked doctrines. But this is no reason why St. Paul's epistles, or any other part of the Scriptures, should be laid aside; for men, left to themselves, pervert every gift of God. Then let us seek to have our minds prepared for receiving things hard to be understood, by putting in practice things which are more easy to be understood. But there must be self-denial and suspicion of ourselves, and submission to the authority of Christ Jesus, before we can heartily receive all the truths of the gospel, therefore we are in great danger of rejecting the truth. And whatever opinions and thoughts of men are not according to the law of God, and warranted by it, the believer disclaims and abhors. Those who are led away by error, fall from their own stedfastness. And that we may avoid being led away, we must seek to grow in all grace, in faith, and virtue, and knowledge. Labour to know Christ more clearly, and more fully; to know him so as to be more like him, and to love him better. This is the knowledge of Christ, which the apostle Paul reached after, and desired to attain; and those who taste this effect of the knowledge of the Lord and Saviour Jesus Christ, will, upon receiving such grace from him, give thanks and praise him, and join in ascribing glory to him now, in the full assurance of doing the same hereafter, for ever.

Your duty, seeing that this is so, is to be ever eagerly expecting the day of God.
then--Some oldest manuscripts substitute "thus" for "then": a happy refutation of the "thus" of the scoffers, 2-Peter 3:4 (English Version, "As they were," Greek, "thus").
shall be--Greek, "are being (in God's appointment, soon to be fulfilled) dissolved"; the present tense implying the certainty as though it were actually present.
what manner of men--exclamatory. How watchful, prayerful, zealous!
to be--not the mere Greek substantive verb of existence (einai), but (huparchein) denoting a state or condition in which one is supposed to be [TITTMANN]. What holy men ye ought to be found to be, when the event comes! This is "the holy commandment" mentioned in 2-Peter 3:2.
conversation . . . godliness--Greek, plural: behaviors (towards men), godlinesses (or pieties towards God) in their manifold modes of manifestation.

Seeing then that all these things are dissolved - To the eye of faith it appears as done already. All these things - Mentioned before; all that are included in that scriptural expression, "the heavens and the earth;" that is, the universe. On the fourth day God made the stars, Genesis 1:16, which will be dissolved together with the earth. They are deceived, therefore, who restrain either the history of the creation, or this description of the destruction, of the world to the earth and lower heavens; imagining the stars to be more ancient than the earth, and to survive it. Both the dissolution and renovation are ascribed, not to the one heaven which surrounds the earth, but to the heavens in general, 2-Peter 3:10, 2-Peter 3:13, without any restriction or limitation. What persons ought ye to be in all holy conversation - With men. And godliness - Toward your Creator.