Beware of false prophets

“Beware of false prophets, who come to you in sheep’s clothing but inwardly are ravenous wolves. You will recognize them by their fruits. Are grapes gathered from thornbushes, or figs from thistles? So, every healthy tree bears good fruit, but the diseased tree bears bad fruit. A healthy tree cannot bear bad fruit, nor can a diseased tree bear good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. Thus you will recognize them by their fruits.” (Matthew 7:15-20 ESV)

“Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world. By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God, and every spirit that does not confess Jesus is not from God. This is the spirit of the antichrist, which you heard was coming and now is in the world already. Little children, you are from God and have overcome them, for he who is in you is greater than he who is in the world. They are from the world; therefore they speak from the world, and the world listens to them. We are from God. Whoever knows God listens to us; whoever is not from God does not listen to us. By this we know the Spirit of truth and the spirit of error.” (1 John 4:1-6 ESV)

“Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints. For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ.
Now I want to remind you, although you once fully knew it, that Jesus, who saved a people out of the land of Egypt, afterward destroyed those who did not believe. And the angels who did not stay within their own position of authority, but left their proper dwelling, he has kept in eternal chains under gloomy darkness until the judgment of the great day-- just as Sodom and Gomorrah and the surrounding cities, which likewise indulged in sexual immorality and pursued unnatural desire, serve as an example by undergoing a punishment of eternal fire.
Yet in like manner these people also, relying on their dreams, defile the flesh, reject authority, and blaspheme the glorious ones. But when the archangel Michael, contending with the devil, was disputing about the body of Moses, he did not presume to pronounce a blasphemous judgment, but said, “The Lord rebuke you.” But these people blaspheme all that they do not understand, and they are destroyed by all that they, like unreasoning animals, understand instinctively. Woe to them! For they walked in the way of Cain and abandoned themselves for the sake of gain to Balaam’s error and perished in Korah’s rebellion. These are hidden reefs at your love feasts, as they feast with you without fear, shepherds feeding themselves; waterless clouds, swept along by winds; fruitless trees in late autumn, twice dead, uprooted; wild waves of the sea, casting up the foam of their own shame; wandering stars, for whom the gloom of utter darkness has been reserved forever.
It was also about these that Enoch, the seventh from Adam, prophesied, saying, “Behold, the Lord comes with ten thousands of his holy ones, to execute judgment on all and to convict all the ungodly of all their deeds of ungodliness that they have committed in such an ungodly way, and of all the harsh things that ungodly sinners have spoken against him.” These are grumblers, malcontents, following their own sinful desires; they are loud-mouthed boasters, showing favoritism to gain advantage.” (Jude 1:3-16 ESV)

“But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction. And many will follow their sensuality, and because of them the way of truth will be blasphemed. And in their greed they will exploit you with false words. Their condemnation from long ago is not idle, and their destruction is not asleep.
For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment; if he did not spare the ancient world, but preserved Noah, a herald of righteousness, with seven others, when he brought a flood upon the world of the ungodly; if by turning the cities of Sodom and Gomorrah to ashes he condemned them to extinction, making them an example of what is going to happen to the ungodly; and if he rescued righteous Lot, greatly distressed by the sensual conduct of the wicked (for as that righteous man lived among them day after day, he was tormenting his righteous soul over their lawless deeds that he saw and heard); then the Lord knows how to rescue the godly from trials, and to keep the unrighteous under punishment until the day of judgment, and especially those who indulge in the lust of defiling passion and despise authority.
Bold and willful, they do not tremble as they blaspheme the glorious ones, whereas angels, though greater in might and power, do not pronounce a blasphemous judgment against them before the Lord. But these, like irrational animals, creatures of instinct, born to be caught and destroyed, blaspheming about matters of which they are ignorant, will also be destroyed in their destruction, suffering wrong as the wage for their wrongdoing. They count it pleasure to revel in the daytime. They are blots and blemishes, reveling in their deceptions, while they feast with you. They have eyes full of adultery, insatiable for sin. They entice unsteady souls. They have hearts trained in greed. Accursed children! Forsaking the right way, they have gone astray. They have followed the way of Balaam, the son of Beor, who loved gain from wrongdoing, but was rebuked for his own transgression; a speechless donkey spoke with human voice and restrained the prophet’s madness.
These are waterless springs and mists driven by a storm. For them the gloom of utter darkness has been reserved. For, speaking loud boasts of folly, they entice by sensual passions of the flesh those who are barely escaping from those who live in error. They promise them freedom, but they themselves are slaves of corruption. For whatever overcomes a person, to that he is enslaved. For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overcome, the last state has become worse for them than the first. For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them. What the true proverb says has happened to them: “The dog returns to its own vomit, and the sow, after washing herself, returns to wallow in the mire.”” (2 Peter 2:1-22 ESV)

“I wish you would bear with me in a little foolishness. Do bear with me! For I feel a divine jealousy for you, since I betrothed you to one husband, to present you as a pure virgin to Christ. But I am afraid that as the serpent deceived Eve by his cunning, your thoughts will be led astray from a sincere and pure devotion to Christ. For if someone comes and proclaims another Jesus than the one we proclaimed, or if you receive a different spirit from the one you received, or if you accept a different gospel from the one you accepted, you put up with it readily enough. Indeed, I consider that I am not in the least inferior to these super-apostles. Even if I am unskilled in speaking, I am not so in knowledge; indeed, in every way we have made this plain to you in all things.
Or did I commit a sin in humbling myself so that you might be exalted, because I preached God’s gospel to you free of charge? I robbed other churches by accepting support from them in order to serve you. And when I was with you and was in need, I did not burden anyone, for the brothers who came from Macedonia supplied my need. So I refrained and will refrain from burdening you in any way. As the truth of Christ is in me, this boasting of mine will not be silenced in the regions of Achaia. And why? Because I do not love you? God knows I do!
And what I am doing I will continue to do, in order to undermine the claim of those who would like to claim that in their boasted mission they work on the same terms as we do. For such men are false apostles, deceitful workmen, disguising themselves as apostles of Christ. And no wonder, for even Satan disguises himself as an angel of light. So it is no surprise if his servants, also, disguise themselves as servants of righteousness. Their end will correspond to their deeds.” (2 Corinthians 11:1-15 ESV)