These people are false apostles. They are deceitful workers who disguise themselves as apostles of Christ. . . . Even Satan disguises himself as an angel of light. So it is no wonder that his servants also disguise themselves as servants of righteousness.
2 CORINTHIANS 11:13–15
"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 licentiousness, and because of them the way of truth will be reviled. And in their greed they will exploit you with false words; from of old their condemnation has not been idle, and their destruction has not been asleep." (2 Peter 2:1–3)
3 As Jesus was sitting on the Mount of Olives, the disciples came to him privately. "Tell us," they said, "when will this happen, and what will be the sign of your coming and of the end of the age?" 4 Jesus answered: "Watch out that no one deceives you. 5 For many will come in my name, claiming, "I am the Christ," and will deceive many. 6 You will hear of wars and rumors of wars, but see to it that you are not alarmed. Such things must happen, but the end is still to come.
--Matthew 24