Zac Poonen emphasizes the testing of David, highlighting how God chose David for his faithfulness and concern for God's glory, contrasting him with Saul, who failed God's tests. David's journey from shepherd to king was marked by his dedication to his earthly duties and his unwavering commitment to honor God's name, especially evident when he faced Goliath. Poonen points out that true servants of God prioritize God's glory over personal comfort, and that such a concern fosters strong faith that can overcome fear. David's life serves as a model for believers to be faithful in their responsibilities and to boldly confront challenges for the sake of God's honor.