In lecture four, we are introduced to the pivotal figure of King David in the Old Testament, who sheds light on the roles of priest, prophet, and king. We examine David as the "sweet singer of the House of Israel," a warrior, and a priest, and discuss how these roles anticipate the fulfillment found in Jesus Christ, the son of David. The lecture also delves into the story of Elijah challenging the priests of Baal, illustrating the importance of worshipping the true God and the call of the prophet Isaiah, which reveals the pattern of grace, acknowledgment of sin, and mission in the spiritual life.