The necessity of holiness in order to enter heaven. Just talking about this won't do - they must live holy. They cannot honestly say that they really have tried to live without sin. They drift along before the tide in a loose, sinful, unhappy, and abominable manner, at which undoubtedly the devil laughs, because it is of all others the surest way to hell. To the necessity of self-denial and living above the world.
Christians ought to show by their own example what the Christian walk is.
That is the most powerful preaching - the kind which shows sinners the great difference between themselves and Christians. Many believe they can best make people accept the truth by bringing religion down to the standards of men. As if the nearer you bring religion to the world, the more likely the world will be to embrace it. And they think they are displaying such wonderful wisdom by taking so much pain not to scare people at the mighty strictness and holiness of the Gospel. This seems reasonable at first, but it is not true.