2 Kefa 2:1

But there were also nevi'ei sheker (false prophets) among Am Yisroel just as also there will be morei sheker among you. These false teachers will secretly bring in heretical doctrines of koferim ba-ikkarim (deniers of fundamentals), producing machshelah (ruin), as these heretics even become meshummad, denying the Ribbono Shel Olam who redeemed them, bringing upon themselves swift destruction.