Matthew 7:15
"Look out for deceiving prophets, who approach you wearing sheep's clothing, but who are [actually] starving wolves in their hearts.
2 Corinthians 11:13
For such men are false apostles; they are deceitful workers, who disguise themselves as [true] apostles of Christ.
2 Peter 2:1-3
But just as there were false prophets among the people before, there will also be false teachers among you [Christians]. They will privately teach harmful doctrines that destroy people [spiritually], by even denying [that Jesus is] the Master, [and thereby] destroying themselves quickly.
1 John 4:1
Loved ones, do not believe [the message of] every spirit [i.e., every person claiming to be a teacher], but test the spirits [i.e., require proof that they and their message are genuine] to see whether they represent God [or not], because many false prophets have begun circulating throughout the world.
Revelation 19:20
But the beast was captured, along with the false prophet [See 16:13], who performed [supernatural] signs in his presence. [He had performed these signs] to deceive those who had received the mark of the beast and those who worshiped his statue. [See 13:15-16]. The beast and the false prophet were both thrown alive into the lake of fire that burns with sulphur.