John Nelson Darby emphasizes the significance of Christ speaking from heaven, contrasting it with His earthly voice. He warns that those who turn away from this heavenly voice will face dire consequences, as it signifies the removal of all that opposes God. The sermon highlights the believer's blessedness in resting on Jesus, who has accomplished salvation and now speaks peace from His position of glory. Darby encourages believers to focus on the eternal promises of God, which cannot be shaken, and to remain vigilant in their faith amidst worldly trials. Ultimately, he reassures that the voice of Jesus brings peace and joy, affirming the believer's identity and security in Him.