1 Corinthians 5:8

Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth (KJV)

Then: What's that? Keep the feast? Corinthians weren't Jews. And I don't see a "Do-it-on-Easter" or "Do-it-on-Sundays" stipulation. Neither did the Corinthians. They got it that Paul meant communion, feasting with Christ. Like it or not, they also knew Paul meant daily. Living without the leaven of carnality (or evil) is a difficult, on-going task. The Corinthians were a long way from engaging in daily battles to meet that goal. Rather they preferred the idea of freedom in Christ, thinking that it meant license to be with him on the throne no matter their lack of growth in meeting his standards.

Now: Matthew Henry advises Christians that keeping the feast means dying to sin, as Christ died for us, and rising to an internal purity. While doing that, no one has time to pronounce petty judgements on fellow believers. Actually, it replaces judgement with compassion and understanding because of personal struggles in working to tramp down the desires of the flesh and ever calling on Christ. Choosing to live without malice and without wickedness, to always be sincere and truthful, is an antidote to a fallen world.

Extra Source: Commentary on the Whole Bible Acts to Revelation Vol VI by Matthew Henry online at http://www.ccel.org/ccel/henry/mhc6.iCor.vi.html