Even when preaching the Word of God does not soften and save and heal, it is not necessarily ineffective. This preaching of the Word may be doing God’s terrible work of judgment. It may be hardening people, and making their ears so dull that they will never want to hear again. There is a judgment in this world – not just in the world to come (Romans 1:24) – and oh, how we should flee from it…. Take heed how you hear! Don’t be cavalier in the hearing of God's Word week after week. If it is not softening and saving and healing and bearing fruit, it is probably hardening and blinding and dulling (see 2 Corinthians 2:16).
John Piper