Keith Simons teaches on Psalm 139, emphasizing the deliberate order of the Psalms and how they connect to God's omniscience and omnipresence. He explains that God knows us intimately, from our thoughts to our actions, and that His presence surrounds us in every situation. Simons highlights the contrast between the proud and the humble, illustrating how God respects the lowly while being distant from the proud. The psalm culminates in a plea for self-examination, urging believers to seek God's guidance and correction in their lives. Ultimately, it is a reflection on God's greatness and our need for His mercy and direction.