6 Your flip and callous arrogance in these things bothers me. You pass it off as a small thing, but it's anything but that. Yeast, too, is a "small thing," but it works its way through a whole batch of bread dough pretty fast.
7 So get rid of this "yeast." Our true identity is flat and plain, not puffed up with the wrong kind of ingredient. The Messiah, our Passover Lamb, has already been sacrificed for the Passover meal, and we are the Unraised Bread part of the Feast. 8 So let's live out our part in the Feast, not as raised bread swollen with the yeast of evil, but as flat bread - simple, genuine, unpretentious.
Matthew Henry's Commentary on 1 Corinthians 5:6-8
Commentary on 1 Corinthians 5:1-8
(Read 1 Corinthians 5:1-8)
The apostle notices a flagrant abuse, winked at by the Corinthians. Party spirit, and a false notion of Christian liberty, seem to have saved the offender from censure. Grievous indeed is it that crimes should sometimes be committed by professors of the gospel, of which even heathens would be ashamed. Spiritual pride and false doctrines tend to bring in, and to spread such scandals. How dreadful the effects of sin! The devil reigns where Christ does not. And a man is in his kingdom, and under his power, when not in Christ. The bad example of a man of influence is very mischievous; it spreads far and wide. Corrupt principles and examples, if not corrected, would hurt the whole church. Believers must have new hearts, and lead new lives. Their common conversation and religious deeds must be holy. So far is the sacrifice of Christ our Passover for us, from rendering personal and public holiness unnecessary, that it furnishes powerful reasons and motives for it. Without holiness we can neither live by faith in him, nor join in his ordinances with comfort and profit.