Its helpful to read Paul and Peter together regarding subjects
“that ye may be mindful of the words which were spoken before by the holy prophets, and of the commandment of us the apostles of the Lord and Saviour: knowing this first, that there shall come in the last days scoffers, walking after their own lusts, and saying, Where is the promise of his coming? for since the fathers fell asleep, all things continue as they were from the beginning of the creation. but the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men. But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day. The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.”
2 Peter 3:2-4, 7-10 KJV
“For yourselves know perfectly that the day of the Lord so cometh as a thief in the night. For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape.”
1 Thessalonians 5:2-3 KJV
“For as in the days that were before the flood they were eating and drinking, marrying and giving in marriage, until the day that Noe entered into the ark, and knew not until the flood came, and took them all away; so shall also the coming of the Son of man be. Watch therefore: for ye know not what hour your Lord doth come.”
Matthew 24:38-39, 42 KJV
It’s part of the doctrine that he could come at any point. Just as they believed them we should believe now it presses us forward into repentance and diligence in Christ vigilance as we grow up
“Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at the cockcrowing, or in the morning: lest coming suddenly he find you sleeping. And what I say unto you I say unto all, Watch.”
Mark 13:35-37 KJV
“Therefore let us not sleep, as do others; but let us watch and be sober.”
1 Thessalonians 5:6 KJV
The Bible teaches believers an urgency towards repentance before it’s too late
“and to you who are troubled rest with us, when the Lord Jesus shall be revealed from heaven with his mighty angels, in flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ: who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power; when he shall come to be glorified in his saints, and to be admired in all them that believe (because our testimony among you was believed) in that day.”
2 Thessalonians 1:7-10 KJV
Notice this is summarizing key points of the gospel
“For the grace of God that bringeth salvation hath appeared to all men, teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly, in this present world; ( the gospel teaches us this ) looking for that blessed hope, and the glorious appearing of the great God and our Saviour Jesus Christ; ( also this tbat he’s coming back again )
who gave himself for us, ( and this also the gospels teach) that he might redeem us from all iniquity, and purify unto himself a peculiar people, zealous of good works.”( indeed the lord also and his apostles teach this )
Titus 2:11-14