T. Austin-Sparks emphasizes the concept of 'Functional Union' within the Body of Christ, illustrating how each member plays a vital role in expressing the personality of Christ. He explains that the Church exists not for self-expression but to manifest Christ's presence and personality, highlighting the importance of interrelatedness, interdependence, and mutual support among believers. Sparks warns against both the exaggeration and neglect of the Body, urging Christians to recognize their responsibility in functioning as part of this living organism. He concludes that Christ's headship is essential for the Body to operate effectively, and that spiritual growth is contingent upon maintaining a strong connection with one another and with Christ. The sermon calls for believers to actively engage in their roles within the Body to fully express Christ's life and purpose.