"Beware of the false prophets, who come to you in sheep’s clothing, but inwardly are ravenous wolves. You will know them by their fruits. Grapes are not gathered from thorn bushes nor figs from thistles, are they? So every good tree bears good fruit, but the bad tree bears bad fruit. A good tree cannot produce bad fruit, nor can a bad tree produce good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. So then, you will know them by their fruits," (Matthew 7:15-20).

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"For there is no good tree which produces bad fruit, nor, on the other hand, a bad tree which produces good fruit. For each tree is known by its own fruit. For men do not gather figs from thorns, nor do they pick grapes from a briar bush. The good man out of the good treasure of his heart brings forth what is good; and the evil man out of the evil treasure brings forth what is evil; for his mouth speaks from that which fills his heart," (Luke 6:43-45).

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"Either make the tree good and its fruit good, or make the tree bad and its fruit bad; for the tree is known by its fruit. You brood of vipers, how can you, being evil, speak what is good? For the mouth speaks out of that which fills the heart. The good man brings out of his good treasure what is good; and the evil man brings out of his evil treasure what is evil. But I tell you that every careless word that people speak, they shall give an accounting for it in the day of judgment. For by your words you will be justified, and by your words you will be condemned," (Matthew 12:33-37).

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"But no one can tame the tongue; it is a restless evil and full of deadly poison. With it we bless our Lord and Father, and with it we curse men, who have been made in the likeness of God; from the same mouth come both blessing and cursing. My brethren, these things ought not to be this way. Does a fountain send out from the same opening both fresh and bitter water? Can a fig tree, my brethren, produce olives, or a vine produce figs? Nor can salt water produce fresh," (James 3:8-12).

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"'I have heard what the prophets have said who prophesy falsely in My name, saying, ‘I had a dream, I had a dream!’ How long? Is there anything in the hearts of the prophets who prophesy falsehood, even these prophets of the deception of their own heart, who intend to make My people forget My name by their dreams which they relate to one another, just as their fathers forgot My name because of Baal? The prophet who has a dream may relate his dream, but let him who has My word speak My word in truth. What does straw have in common with grain?' declares the Lord. 'Is not My word like fire?' declares the Lord, 'and like a hammer which shatters a rock? Therefore behold, I am against the prophets,' declares the Lord, 'who steal My words from each other. Behold, I am against the prophets,' declares the Lord, 'who use their tongues and declare, ‘The Lord declares.’ Behold, I am against those who have prophesied false dreams,' declares the Lord, 'and related them and led My people astray by their falsehoods and reckless boasting; yet I did not send them or command them, nor do they furnish this people the slightest benefit,' declares the Lord," (Jeremiah 23:25-32).

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"for false Christs and false prophets will arise, and will show signs and wonders, in order to lead astray, if possible, the elect. But take heed; behold, I have told you everything in advance," (Mark 13:22-23).

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"But false prophets also arose among the people, just as there will also be false teachers among you, who will secretly introduce destructive heresies, even denying the Master who bought them, bringing swift destruction upon themselves. Many will follow their sensuality, and because of them the way of the truth will be maligned; and in their greed they will exploit you with false words; their judgment from long ago is not idle, and their destruction is not asleep," (2 Peter 2:1-3).

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"Beloved, do not believe every spirit, but test the spirits to see whether they are from God, because 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, of which you have heard that it is coming, and now it is already in the world. You are from God, little children, and have overcome them; because greater is He who is in you than he who is in the world. They are from the world; therefore they speak as from the world, and the world listens to them. We are from God; he who knows God listens to us; he who 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).

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"But even if we or an angel from heaven should proclaim to you a gospel contrary to what we proclaimed to you, let that one be accursed! As we have said before, so now I repeat, if anyone proclaims to you a gospel contrary to what you received, let that one be accursed!" (Galatians 1:8-9).

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"If a prophet or a dreamer of dreams arises among you and gives you a sign or a wonder, and the sign or the wonder comes true, concerning which he spoke to you, saying, ‘Let us go after other gods (whom you have not known) and let us serve them,’ you shall not listen to the words of that prophet or that dreamer of dreams; for the Lord your God is testing you to find out if you love the Lord your God with all your heart and with all your soul. You shall follow the Lord your God and fear Him; and you shall keep His commandments, listen to His voice, serve Him, and cling to Him. But that prophet or that dreamer of dreams shall be put to death, because he has counseled rebellion against the Lord your God who brought you from the land of Egypt and redeemed you from the house of slavery, to seduce you from the way in which the Lord your God commanded you to walk. So you shall purge the evil from among you," (Deuteronomy 13:1-5).

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"But the prophet who speaks a word presumptuously in My name which I have not commanded him to speak, or which he speaks in the name of other gods, that prophet shall die.’ You may say in your heart, ‘How will we know the word which the Lord has not spoken?’ When a prophet speaks in the name of the Lord, if the thing does not come about or come true, that is the thing which the Lord has not spoken. The prophet has spoken it presumptuously; you shall not be afraid of him," (Deuteronomy 18:20-22).

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"Whosoever, therefore, shall come and teach you all these things that have been said before, receive him; but if the teacher himself be perverted and teach a different doctrine to the destruction thereof, hear him not.," (Didache, Chapter 11).

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"Every one that teaches anything beyond what is commanded, though he be [deemed] worthy of credit, though he be in the habit of fasting, though he live in continence, though he work miracles, though he have the gift of prophecy, let him be in thy sight as a wolf in sheep’s clothing," (Pseudo-Ignatius, Epistle to Hero the Deacon, Chapter 2).1

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"But let us rather be mindful of the sayings of the Lord, and of the letters of the apostles; for they have both told us beforehand that there shall be heresies, and have given us, in anticipation, warnings to avoid them; and inasmuch as we are not alarmed because they exist, so we ought not to wonder that they are capable of doing that, on account of which they must be shunned. The Lord teaches us that many 'ravening wolves shall come in sheep’s clothing.' Now, what are these sheep’s clothing’s, but the external surface of the Christian profession? Who are the ravening wolves but those deceitful senses and spirits which are lurking within to waste the flock of Christ? Who are the false prophets but deceptive predictors of the future? Who are the false apostles but the preachers of a spurious gospel?" (Tertullian, The Prescription Against Heretics, Chapter 4).