The design here is to remind of Christ's final coming to judgement.
He will appear unexpectedly, when the present frame of nature will be dissolved by fire.
From thence is inferred the need for holiness, and stedfastness in the faith.
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, Ps 55:19. What he never has done, they fancy he never can do, or never will do.
Had these scoffers considered the dreadful vengeance with which God swept away a whole world of ungodly men at once, surely they would not have scoffed at his threatening an equally terrible judgment. The heavens and the earth which now are, by the same word, it is declared, will be destroyed by fire. This is as sure to come, as the truth and the power of God can make it. Christians are here taught and established in the truth of the coming of the Lord. Though, in the account of men, there is a vast difference between one day and a thousand years, yet, in the account of God, there is no difference. All things past, present, and future, are ever before him: the delay of a thousand years cannot be so much to him, as putting off any thing for a day or for an hour is to us. If men have no knowledge or belief of the eternal God, they will be very apt to think him such as themselves. How hard is it to form any thoughts of eternity! What men count slackness, is long-suffering, and that to us-ward; it is giving more time to hisown people, to advance in knowledge and holiness, and in the exercise of faith and patience, to abound in good works, doing and suffering what they are called to, that they may bring glory to God. Settle therefore in your hearts that you shall certainly be called to give an account of all things done in the body, whether good or evil. And let a humble and diligent walking before God, and a frequent judging of yourselves, show a firm belief of the future judgment, though many live as if they were never to give any account at all. This day will come, when men are secure, and have no expectation of the day of the Lord. The stately palaces, and all the desirable things wherein wordly-minded men seek and place their happiness, shall be burned up; all sorts of creatures God has made, and all the works of men, must pass through the fire, which shall be a consuming fire to all that sin has brought into the world, though a refining fire to the works of God's hand. What will become of us, if we set our affections on this earth, and make it our portion, seeing all these things shall be burned up? Therefore make sure of happiness beyond this visible world.
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.