In his sermon, Pastor Jamie Self at Grace Church looks at Matthew 6:1-4 to emphasize the importance of practicing righteousness for God's glory rather than seeking human approval. He discusses the dangers of hypocritical behavior and the temptation to seek validation from others rather than from God. Drawing from personal experience and John Piper's teachings, he encourages believers to live in constant awareness of God's presence, focusing on God's approval and living out their faith authentically.