Galatians 5:9 - Clarke's commentary and critical notes on the Bible

A little leaven leaveneth the whole lump. A little leaven leaveneth the whole lump - A proverbial expression, see 1 Corinthians 5:6, very aptly applied to those who receive the smallest tincture of false doctrine, relative to the things essential to salvation, which soon influences the whole conduct, so that the man becomes totally perverted. They might have argued, "It is a small thing, and should not be made a subject of serious controversy, whether we be circumcised or not." Granted, that in itself it is a small matter; but, as every man who is circumcised is a debtor to do the whole law, Galatians 5:3, then your circumcision leads necessarily to your total perversion; as the little portion of leaven, mixed with the batch, soon leavens the whole lump.