2 Peter 3:14-18
14 Wherefore, beloved, seeing that ye look for such things, be diligent that ye may be found of him in peace, without spot, and blameless.
15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;
16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
17 Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.
18 But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory both now and for ever. Amen.
The Grace New Testament Commentary - 2 Peter 3:14, 3:17
3:14 Since the Day of the Lord was to arrive without warning like a thief in the night (see vv 1-10a), the Lord Jesus might come at any time. In view of that, the readers ought to be careful that when He came He would find them in harmony with one another (in peace) and free from moral and spiritual defilement. The words without spot and blameless do not, of course, indicate sinlessness, but rather lives lived free of the general depravity and corruptness all around them, especially of the sort encouraged by the licentiousness of the false teachers.
3:17 The deplorable example of the untaught and unstable ought to be a warning to the readers not to be similarly deceived by the error of the wicked. Peter again no doubt has in mind the coming false teachers whose theology not only involves twisting the Scriptures but is also motivated by their own corrupt desires. Peter does not want the readers to forget that false doctrine and depravity often go hand in hand.
The beloved readers ought not to be led astray in this manner and thus fall from their present state of spiritual steadfastness. Peter's view of the readers is positive at this point and he wishes them to maintain their spiritual stability in God's truth. However, his realism about the spiritual dangers they face is refreshing. It contrasts sharply with the readiness of many today to construe such a fall as evidence of an unregenerate condition.
Charles Bing - Grace, Salvation, and Discipleship - Be Diligent to be Found Blameless, 2 Peter 3:14-18
(Salvation) Interpretation: Diligence in holiness results in eternal salvation.
(Discipleship) Interpretation: Diligence in holiness prepares Christians to meet the Lord.
This passage is a good summary conclusion of the epistle and themes we have already discussed, so there is no great need to re-argue Peter's points. Verse 14 looks forward to the coming Day of the Lord as a motivation to live godly in the present. Its exhortation reminds us of 2 Peter 1:5-11, which speaks of diligence in adding virtues to our faith so that we can have a high-quality reception into Christ's kingdom. The phrase "without spot and wrinkle" does not speak of imputed righteousness, but a blameless life which should be the readers' goal when they are presented to Jesus Christ at the Judgment Seat of Christ (cf. Eph. 5:27).
From a (Discipleship) perspective, we would also see that it is possible for believers ("beloved") to fail in their steadfast stand in Christ and be deceived by the error of false teaching (v. 17). This does not forfeit their salvation or prove they were never saved. It proves that Christians can stop growing and even contradict the truth they know. In this way, this passage reinforces the interpretation of 2 Peter 2, which we have just discussed. Peter exhorts his readers to continue steadfastly in the truth so that they will not be led away into error.
The best preventative for error is to be diligent in growing "in the grace and knowledge of our Lord and Savior Jesus Christ" (v. 18). These are not casual words, because error usually comes first in attacks against salvation by grace alone through faith alone, and attacks upon the person and work of Christ. The more we know God's grace and God's Son, the less we are vulnerable to the error of false teaching.