Preaching is dangerous; most of all for the preachers. There is a moral and spiritual expectation that what they say is what they do (James 3:1-2).
By asking these four searching questions, Paul affirms Jesus' Sermon on the Mount (Matthew 5:21-22, Matthew 5:27-28). Pleasing God is not just about actions but attitudes as well, even the hidden things of the heart. Jewish-background believers, who boasted about their Bible knowledge, despised the Gentile Christians. But they should have been ashamed: even the unbelievers knew their lifestyles were inconsistent.