Mat 7:15,22-23 (Wey) "Beware of the false teachers--men who come to you in sheep's fleeces, but beneath that disguise they are ravenous wolves... Many will say to me on that day, 'Master, Master, have we not prophesied in Thy name, and in Thy name expelled demons, and in Thy name performed many mighty works?' And then I will tell them plainly, 'I never knew you: begone from me, you doers of wickedness.'"
Ex 20:7 (YLT) "Thou dost not take up the name of Jehovah thy God for a vain thing, for Jehovah acquitteth not him who taketh up His name for a vain thing."
2 Cor 11:13-15 (NIV) For such men are false apostles, deceitful workmen, masquerading as apostles of Christ. And no wonder, for Satan himself masquerades as an angel of light. It is not surprising, then, if his servants masquerade as servants of righteousness. Their end will be what their actions deserve.
Acts 8:9-11 (NIV) Now for some time a man named Simon had practiced sorcery in the city and amazed all the people of Samara. He boasted that he was someone great, and all the people, both high and low, gave him their attention and exclaimed, "This man is the divine power known as the Great Power." They followed him because he had amazed them for a long time with his magic.
Jer 23:25-32 (NIV) "I have heard what the prophets say who prophesy lies in my name. They say, 'I had a dream! I had a dream!' How long will this continue in the hearts of these lying prophets, who prophesy the delusions of their own minds? They think the dreams they tell one another will make my people forget my name, just as their fathers forgot my name through Baal worship. Let the prophet who has a dream tell his dream, but let the one who has my word speak it faithfully. For what has straw to do with grain?" declares the Lord. "Is not my word like fire," declares the Lord, "and like a hammer that breaks a rock in pieces? Therefore," declares the Lord, "I am against the prophets who steal from one another words supposedly from me. Yes," declares the Lord, "I am against the prophets who wag their own tongues and yet declare, 'The Lord declares.' Indeed, I am against those who prophesy false dreams," declares the Lord. "They tell them and lead my people astray with their reckless lies, yet I did not send or appoint them. They do not benefit these people in the least," declares the Lord.
Eze 13:1-8 (NIV) The word of the Lord came to me: "Son of man, prophesy against the prophets of Israel who are now prophesying. Say to those who prophesy out of their own imagination: 'Hear the word of the Lord! This is what the Sovereign Lord says: Woe to the foolish prophets who follow their own spirit and have seen nothing! Your prophets, O Israel, are like jackals among ruins. You have not gone up to the breaks in the wall to repair it for the house of Israel so that it will stand firm in the battle on the day of the Lord. Their visions are false and their divinations a lie. They say, "The Lord declares," when the Lord has not sent them; yet they expect their words to be fulfilled. Have you not seen false visions and uttered lying divinations when you say, "The Lord declares," though I have not spoken? "Therefore this is what the Sovereign Lord says: Because of your false words and lying visions, I am against you, declares the Sovereign Lord."
This whole chapter is worth reading in your own Bible. Here is another sample.
Eze 13:22-23 (NIV) "Because you disheartened the righteous with your lies, when I had brought them no grief, and because you encouraged the wicked not to turn from their evil ways and so save their lives, therefore you will no longer see false visions or practice divination. I will save my people from your hands. And then you will know that I am the Lord."
2 Pet 2:1-3 (Wey) But there were also false prophets among the people, as there will be teachers of falsehood among you also, who will cunningly introduce fatal divisions, disowning even the Sovereign Lord who has redeemed them, and bringing on themselves swift destruction. And in their immoral ways they will have many eager disciples, through whom religion will be brought into disrepute. Thirsting for riches, they will trade on you with their canting talk. From of old their judgment has been working itself out, and their destruction has not been slumbering.
2 Pet 2:1-3 (NIV) But there were also false prophets among the people, just as there will be false teachers among you. They will secretly introduce destructive heresies, even denying the sovereign Lord who bought them--bringing swift destruction on themselves. Many will follow their shameful ways and will bring the way of truth into disrepute. In their greed these teachers will exploit you with stories they have made up. Their condemnation has long been hanging over them, and their destruction has not been sleeping.
John 8:39-44 (NIV) "Abraham is our father," they answered. "If you were Abraham's children," said Jesus, "then you would do the things Abraham did... Abraham did not do such things. You are doing the things your own father does." "We are not illegitimate children," they protested. "The only Father we have is God himself." Jesus said to them, "If God were your Father, you would love me, for I came from God and now am here. I have not come on my own; but he sent me. Why is my language not clear to you? Because you are unable to hear what I say. You belong to your father, the devil, and you want to carry out your father's desire..."
Isa 47:8-11 (NIV) "Now then, listen, you wanton creature, lounging in your security and saying to yourself, 'I am, and there is none besides me. I will never be a widow or suffer the loss of children.' Both of these will overtake you in a moment, on a single day: loss of children and widowhood. They will come upon you in full measure, in spite of your many sorceries and all your potent spells. You have trusted in your wickedness and have said, 'No one sees me.' Your wisdom and knowledge mislead you when you say to yourself, 'I am, and there is none besides me.' Disaster will come upon you, and you will not know how to conjure it away..."
Rev 18:6-8 (NIV) "... Mix her a double portion from her own cup. Give her as much torture and grief as the glory and luxury she gave herself. In her heart she boasts, 'I sit as queen; I am not a widow, and I will never mourn.' Therefore in one day her plagues will overtake her: death, mourning and famine..."