In this sermon, the speaker emphasizes the importance of filling one's heart with the Word of God rather than simply avoiding evil. He references the story of a demon being cast out and returning with seven others to illustrate the need for a filled and clean heart. The speaker encourages meditating on the law of the Lord day and night, comparing the result to a tree planted by rivers of water that prospers in all endeavors. The sermon also touches on the qualities of a godly person, such as having clean hands and a pure heart, seeking guidance from the Lord, and being set apart for God's purposes.