There is not a little vagueness as to ecclesiastical defilement, which God's word dispels. Danger lurks on both sides of the truth, whether from lack of care or from misdirected zeal.
On the one hand it is ungodly to quench hatred of error or of evil by making unity everything. For what communion hath light with darkness? And what concord hath Christ with Belial? 2 Cor. 6.
On the other hand it is unbelief to abandon unity because of the simple entrance of evil, however heinous. 1 Corinthians is the standing witness against such unwarrantable haste. Yet what more flagrant than the evil denounced in 1 Cor. 5? Even the heathen would not tolerate it. Notwithstanding the apostle neither severs himself nor disowns them. He censures their state and demands the putting out of the leaven, so as to vindicate the Lord and clear themselves. What disqualifies is the refusal to hear His voice, the rejection of adequate testimony in His name. So the assembly if faithful ceases to say “brother,” and designates the evil-doer as “wicked.” When repentant, the apostle charges them to confirm love to him.
Can any saint doubt that, if the Corinthians had disobeyed the apostolic command, they must have become a leavened lump? For the church to bind up evil with the Lord's name by glossing it over is to judge itself no longer fit to be called God's church: holy discipline is the indispensable condition of its recognizable status and title. For God is not mocked.
Evil doctrine is yet worse and more dangerous to others; it lowers Christ or His work. So we read in Galatians that their adding a Jewish element is. vehemently rejected and designated as “leaven,” no less than immorality. What can be more unspiritual (not to say faithless) than to treat it now with more indulgence?