Pastor Darren Casper's sermon, "The Power of Hearing Jesus," based on Mark 4:1-20, emphasizes the significance of receiving and understanding God's Word. Through the parable of the sower, Jesus illustrates how different types of soil represent various human hearts and their receptiveness to His message. The sermon underscores the transformative power of God's Word when it is welcomed into our lives. It challenges believers to cultivate good soil in their hearts to produce abundant spiritual fruit.