Watch out for false prophets for they come to you in sheep's clothing, but inwardly they are ferocious wolves Mt 7:15

But there are also false prophets among the people, even as there are false teachers among you who will secretly bring in destructive heresies, even denying the Lord who brought them, and bring upon themselves swift destruction. 2 Pet 2:1

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. 1 Jn 4:1