Galatians 5:7-9

You were running (the race) well; who has interfered and prevented you from obeying the truth? This (deceptive)persuasion is not from Him who called you (to freedom in Christ). A little leaven (a slight inclination to error, or a few false teachers) leavens the whole batch (it perverts the concept of faith and misleads the church).

We are not to believe everything we hear or see but test what is before us against the Word of God. The Word is our truth and guide, given to us to sift what is false against the truth. An error in the truth of God’s Word that slips into our lives will lead us away from God.