When our hearts are rebellious, they hinder God from working within us. In the Gospel we are told that no mighty deeds could be worked in the town because of their lack of faith. They heard Jesus' wisdom and marveled at it. But, instead of those words being accepted and becoming the source of miracles, they were rejected. Why? Because the hearts of the people were hardened.
The Psalms say, "If today you hear his voice, harden not your heart." We cannot break through the concrete of our own hearts. We can only ask Jesus to take away our stony hearts and to put a new heart within us. Today the Lord is offering a new heart. Rebellion against the Lord and his commands leads to a heart that his hardened, distant from God, and miserable. When we rebel against God, his word, his commands, and his Church, we act against our very selves. We destroy ourselves. The heart that welcomes God's word is a heart in which Jesus performs mighty deeds.
If today you hear his voice, harden not your heart.