Galatians 5:9

Leaven is that small portion of fermented dough which is introduced into the fresh lump of dough, and communicates lightness to the whole mass. It is employed figuratively in Scripture to denote the working of both good and bad influences, and is used both of persons and of principles or teaching comp. Matthew 16:12; Luke 13:21. There is a reference, sometimes tacit, sometimes express (1 Corinthians 5:8), to the typical prohibition of the use of leaven in the law of Moses, Exodus 12:15-20; Exodus 12:34. This verse, which occurs again, 1 Corinthians 5:6, seems to have passed into a proverb. Therethe Apostle is condemning the toleration of a single act of open immorality in a member of the Church of Christ. It was the concession of a principle, and whether it be followed by other similar acts or not, the standard of Christian morality will be lowered, and a laxity of tone will gradually pervade the spirit, and degrade the practice, of those who are called -not unto uncleanness but unto holiness". Herethe warning is against the insidious nature of the false teaching of the Judaizing leaders. The difference between that teaching and -the truth of the Gospel" may appear inconsiderable, and the teachers themselves may be insignificant in numbers or in authority. But error, once admitted, is a virus which will gradually spread and poison the whole system of doctrine, or the whole spiritual life of the individual or of the Church.