Jesus warned us about the last days when false ministers and false Christians would come in HIS name deceiving many:
Matthew 24
3 And as HE sat upon the mount of Olives, the disciples came unto Him privately, saying, Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world?
4 And Jesus answered and said unto them, Take heed that no man deceive you.
5 For many shall come in MY name, saying, I am Christ; and shall deceive many.
(Ministers and individuals in churches will come saying "Jesus is Lord" and because they say that, many will accept them and they will deceive "many".)
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Paul calls them "angels of light":
II Corinthians 11
2 For I am jealous over you with godly jealousy: for I have espoused you to one husband, that I may present you as a chaste virgin to Christ.3 But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
4 For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear with him.
13 For such are false apostles, deceitful workers, transforming themselves into the apostles of Christ.
14 And no marvel; for Satan himself is transformed into an angel of light.
15 Therefore it is no great thing if his ministers also be transformed as the ministers of righteousness; whose end shall be according to their works.
2 And many shall follow their pernicious ways; by reason of whom the way of truth shall be evil spoken of.
3 And through covetousness shall they with feigned words make merchandise of you: whose judgment now of a long time lingereth not, and their damnation slumbereth not.
12 But these, as natural brute beasts, made to be taken and destroyed, speak evil of the things that they understand not; and shall utterly perish in their own corruption;
13 And shall receive the reward of unrighteousness, as they that count it pleasure to riot in the day time. Spots they are and blemishes, sporting themselves with their own deceivings while they feast with you;
14 Having eyes full of adultery, and that cannot cease from sin; beguiling unstable souls: an heart they have exercised with covetous practices; cursed children:
15 Which have forsaken the right way, and are gone astray, following the way of Balaam the son of Bosor, who loved the wages of unrighteousness;
16 But was rebuked for his iniquity: the dumb ass speaking with man's voice forbad the madness of the prophet.
17 These are wells without water, clouds that are carried with a tempest; to whom the mist of darkness is reserved for ever.
18 For when they speak great swelling words of vanity, they allure through the lusts of the flesh, through much wantonness, those that were clean escaped from them who live in error.
20 For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning.
21 For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them.
22 But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire.
4 For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ.
13 Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever.
18 How that they told you there should be mockers (imitators/copying others) in the last time, who should walk after their own ungodly lusts.
19 These be they who separate themselves, sensual, having not the Spirit.
5 But all their works they do for to be seen of men: they make broad their phylacteries, and enlarge the borders of their garments,
6 And love the uppermost rooms at feasts, and the chief seats in the synagogues,
7 And greetings in the markets, and to be called of men, Rabbi, Rabbi.
8 But be not ye called Rabbi: for one is your Master, even Christ; and all ye are brethren.
9 And call no man your father upon the earth: for one is your Father, which is in heaven.
10 Neither be ye called masters: for one is your Master, even Christ.
11 But he that is greatest among you shall be your servant.
12 And whosoever shall exalt himself shall be abased; and he that shall humble himself shall be exalted.
13 But woe unto you, scribes and Pharisees, hypocrites! for ye shut up the kingdom of heaven against men: for ye neither go in yourselves, neither suffer ye them that are entering to go in.
14 Woe unto you, scribes and Pharisees, hypocrites! for ye devour widows' houses, and for a pretence make long prayer: therefore ye shall receive the greater damnation.
15 Woe unto you, scribes and Pharisees, hypocrites! for ye compass sea and land to make one proselyte, and when he is made, ye make him twofold more the child of hell than yourselves.
3 Without natural affection, trucebreakers, false accusers, incontinent, fierce, despisers of those that are good,
4 Traitors, heady, highminded, lovers of pleasures more than lovers of God;
13 But he that shall endure unto the end, the same shall be saved.
15 And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus.
16 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:
17 That the man of God may be perfect, throughly furnished unto all good works.