Mathew 12: 38-41 "Then some of the Pharisees and teachers of the law said to him, “Teacher, we want to see a sign from you.” He answered, “A wicked and adulterous generation asks for a sign! But none will be given it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth. The men of Nineveh will stand up at the judgment with this generation and condemn it; for they repented at the preaching of Jonah, and now something greater than Jonah is here."
Matthew 24: 3-14; 24-25 “As He was sitting on the Mount of Olives, the disciples came to Him privately, saying, "Tell us, when will these things happen, and what will be the sign of Your coming, and of the end of the age?" And Jesus answered and said to them, "See to it that no one misleads you. For many will come in My name, saying, 'I am the Christ,' and will mislead many. You will be hearing of wars and rumors of wars. See that you are not frightened, for those things must take place, but that is not yet the end. For nation will rise against nation, and kingdom against kingdom, and in various places there will be famines and earthquakes. But all these things are merely the beginning of birth pangs. Then they will deliver you to tribulation, and will kill you, and you will be hated by all nations because of My name. At that time many will fall away and will betray one another and hate one another. Many false prophets will arise and will mislead many. Because lawlessness is increased, most people's love will grow cold. But the one who endures to the end, he will be saved. This gospel of the kingdom shall be preached in the whole world as a testimony to all the nations, and then the end will come. (Vs. 24): For false Christs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect. (25) Behold, I have told you in advance.”
2 Peter 2:1-3 “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.”
Romans 16:18 “For such people are not serving our Lord Christ, but their own appetites. By smooth talk and flattery they deceive the minds of naive people.”
2 Corinthians 2:17 “Unlike so many, we do not peddle the word of God for profit. On the contrary, in Christ we speak before God with sincerity, as those sent from God.”
2 Corinthians 11:13-15 “For such men are false apostles, deceitful workers, disguising themselves as apostles of Christ. No wonder, for even Satan disguises himself as an angel of light. Therefore it is not surprising if his servants also disguise themselves as servants of righteousness, whose end will be according to their deeds.”
-This article by Steven Kozar