John Nelson Darby explores the profound themes in Luke 9, emphasizing the identity of Jesus as the Son of Man and the necessity of self-denial for His followers. He highlights the significance of the Transfiguration, where Jesus reveals His glory, and the call for disciples to take up their cross daily. Darby stresses the importance of faith in recognizing Christ's power and the need to prioritize spiritual over earthly ties, illustrating the rejection Jesus faced and the implications for those who follow Him. The sermon concludes with a call to embrace the cross and the heavenly calling, reminding believers of the eternal significance of their choices in light of Christ's sacrifice.