2 Peter 3:3

To quicken and excite us to a serious minding and firm adhering to what God has revealed to us by the prophets and apostles, we are told that there will be scoffers, men who will make a mock of sin, and of salvation from it. God's way of saving sinners by Jesus Christ is what men will scoff at, and that in the last days, under the gospel. This indeed may seem very strange, that the New Testament dispensation of the covenant of grace, which is spiritual and therefore more agreeable to the nature of God than the Old, should be ridiculed and reproached; but the spirituality and simplicity of New Testament worship are directly contrary to the carnal mind of man, and this accounts for what the apostle seems here to hint at, namely, that scoffers shall be more numerous and more bold in the last days than ever before. Though in all ages those who were born and walked after the flesh persecuted, reviled, and reproached those who were born and did walk after the Spirit, yet in the last days there will be a great improvement in the art and impudence of bantering serious godliness, and those who firmly adhere to the circumspection and self-denial which the gospel prescribes. This is what is mentioned as a thing well known to all Christians, and therefore they ought to reckon upon it, that they may not be surprised and shaken, as if some strange thing happened unto them.

— Matthew Henry's Concise Commentary (public domain)

Knowing this first--from the word of the apostles. shall come--Their very scoffing shall confirm the truth of the prediction. scoffers--The oldest manuscripts and Vulgate add, "(scoffers) in (that is, 'with') scoffing." As Rev 14:2, "harping with harps." walking after their own lusts-- (Pe2 2:10; Jde 1:16, Jde 1:18). Their own pleasure is their sole law, unrestrained by reverence for God.

— Jamieson-Fausset-Brown Commentary (public domain)