T. Austin-Sparks emphasizes the necessity of becoming a heavenly people to truly possess God's inheritance, as illustrated by Joshua's encounter with the Prince of the Lord's host. He explains that the journey to heavenly fullness requires surrender to the Lordship of the Holy Spirit, which leads to spiritual conflict and growth. The sermon highlights that true possession of the heavenly land is not merely theoretical but requires an actual, lived experience of faith and obedience. Sparks warns against the dangers of earthly attachments that hinder spiritual progress and stresses the importance of maintaining a heavenly position in faith. Ultimately, he calls for believers to recognize the Holy Spirit's commitment to God's eternal purpose rather than their own plans.