"Holiness is not an option; it is a requirement. But this is not a threat. It's a promise. What God began he will finish (Phil. 1:6). In Christ we are already holy, righteous, sanctified, reconciled (1 Corinthians 1:30). Now we are called to live what we are, not to become what we are not yet."
Quoted from his book "Christ the Lord," and taken from the What's Best Next website.