C.H. Spurgeon addresses the undecided individuals in his sermon 'Elijah's Appeal to the Undecided,' urging them to make a definitive choice between serving Jehovah and Baal. He emphasizes the absurdity of trying to serve two masters and challenges the congregation to consider how long they will continue to waver in their faith. Spurgeon points out that true belief must be reflected in one's actions, and he calls for a commitment to God based on His sovereignty rather than personal gain. He warns that indecision will ultimately lead to judgment, and he implores the listeners to seek the Holy Spirit's guidance to make a firm decision for God.