T. Austin-Sparks emphasizes the theme of spiritual enlargement through the biblical account of Elisha succeeding Elijah, highlighting the importance of being filled with the Holy Spirit to maintain the testimony of Jesus. He draws parallels between the Old Testament stories and the New Testament, illustrating how God's call for fullness and enlargement applies to the Church today. Sparks discusses three key incidents: the widow's oil, Naaman's healing, and the sons of the prophets, each demonstrating the necessity of being empty vessels for God's abundant work. He urges believers to embrace a broader vision and ministry, free from limitations and exclusivity, to fulfill their calling in Christ. Ultimately, he calls for a deeper understanding of spiritual fullness and the expansive nature of God's grace.