Simply put, this verse is a warning against unbelief…a stubborn attitude and unwillingness to be receptive to the voice of the Holy Spirit…or as Isaiah 6:10 calls it, a calloused heart, dull ears, and closed eyes. Either way, this hardening of the heart mutes the very voice of Him who is convicting, wooing, and persuading us towards obedience and right standing with God. The Holy Spirit is persistent, but as our conscience becomes more and more hardened to the sound of His voice, it’s easily drowned out by the world.