Galatians 5:6-10

For [if we are] in Christ Jesus neither circumcision nor uncircumcision means anything, but only faith activated and expressed and working through love. 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]. I have confidence in you in the Lord that you will adopt no other view [contrary to mine on the matter]; but the one who is disturbing you, whoever he is, will have to bear the penalty.