William Burkitt on Galatians 5:8

As if the apostle had said, "this judaizing opinion and practice of yours, this persuasion of the necessity of your being circumcised, and obeying the law of Moses; this new doctrine, so contrary to the spirit of the gospel, and the design of Christianity; was never taught you either by God or myself, or any other faithful minister of Jesus Christ, who first converted you to the faith; but it is a mere delusion of Satan, and his emissaries the false apostles: and do not think this a small matter: let not circumcision seem a little thing to you; and let not these judaizing teachers be disregarded by you as inconsiderable, because they are few in number, for they are like to leaven; and ye know very well that a little leaven leaveneth the whole lump; intimating, that a few false teachers, and a little of error and false doctrine, crept into the congregation and church of Christ, may do unspeakable mischief by speedily infecting the whole church, as a little leaven (to error is compared) leaveneth the whole lump.