Romans 16:17-18

17I urge you, brothers and sisters, to keep your eyes on those who cause dissensions and create obstacles or introduce temptations [for others] to commit sin, [acting in ways] contrary to the doctrine which you have learned. Turn away from them.

18For such people do not serve our Lord Christ, but their own appetites and base desires. By smooth and flattering speech they deceive the hearts of the unsuspecting [the innocent and the naive].