3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, (church groups will fall away from scripture) and that man of sin (a spirit reigning over these church groups that fall away from scripture) be revealed, the son of perdition;
4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God. (antichrist within the churches themselves exalting himself and others above the scriptures, above God, in the churches ... removing scriptures and setting up another gospel to please humans in the congregation and to allow sin to reign in the church groups)
5 Remember ye not, that, when I was yet with you, I told you these things? 6 And now ye know what withholdeth that he might be revealed in his time.
7 For the mystery of iniquity doth already work (Paul & John both spoke of antichrist working in churches in their time ... I Jn. 2 for John's comments / Acts 20 for Paul's warning) : only he who now letteth will let, until he be taken out of the way. 8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: 9 Even him, whose coming is after the working of Satan with all power and signs and lying wonders, 10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
11 And for this cause God shall send them strong delusion, that they should believe a lie: 12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
13 But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth: 14 Whereunto he called you by our gospel, to the obtaining of the glory of our Lord Jesus Christ.
15 Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle.
16 Now our Lord Jesus Christ himself, and God, even our Father, which hath loved us, and hath given us everlasting consolation and good hope through grace, 17 Comfort your hearts, and stablish you in every good word and work.
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Concerning antichrist in the churches:
Paul says ... Acts 20 ... 25 And now, behold, I know that ye all, among whom I have gone preaching the kingdom of God, shall see my face no more. 26 Wherefore I take you to record this day, that I am pure from the blood of all men. 27 For I have not shunned to declare unto you all the counsel of God.
28 Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood. 29 For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock. 30 Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them.
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John says ... I Jn. 2 ... 18 Little children, it is the last time:and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time. 19 They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us:but they went out, that they might be made manifest that they were not all of us.
(Antichrist spirit in people coming into the church group in day of John.)
anti-christ / opposite to Christ / opposing Christ, The Word