Matthew 7:15-16

Beware of the false prophets, (teachers) who come to you dressed as sheep but inwardly are ravenous wolves. By their fruit you will recognize them (that is by their contrived doctrine and self-focus). Do people pick grapes from thorn bushes or figs from thistles?

We are to have strong bible knowledge to understand when someone is teaching false doctrine. We are to test what we hear and make sure it lines up with the word of God. God wants to keep us on the clear path to Him.  The devil will twist scripture to deceive and discourage us away from God.