Read Galatians 5.
Paul continued passionately, here in Galatians 5, to argue that the Galatians must not try to mix faith in Christ with obedience to the Law of Moses (vv. 3-6).
Verses 7-10 are a slight parenthesis in Paul’s argument. Paul stopped teaching about our freedom in Christ (vv. 1, 13) and began to wonder in print about who was responsible for the false teaching that had invaded their church (v. 7). In verse 9 he wrote, “A little yeast works through the whole batch of dough.” In other words, if the church tolerates just a little false doctrine, false doctrine will eventually pervade the entire church. Like cancer cells, false doctrine consumes the body of Christ slowly, but steadily.
Also like cancer, false doctrine is often unseen and undetected for a long time, sometimes until it is too late. Paul wrote this letter like a spiritual surgeon, seeking to cut out the spreading cells of false doctrine before it metastasized and killed the whole body.
False doctrine has existed in every age of humanity and, in our digital world, we have access to more of it than ever. Have you been sampling false teaching through TV broadcasts, books, podcasts, or online videos? Remember that it only takes “a little yeast” (v. 9) to leaven the entire loaf. We must be on guard, then. We must test everything against the teaching of scripture and reject everything that conflicts with God’s word.