T. Austin-Sparks emphasizes the paramount importance of having 'Christ fully formed in you,' as articulated in Galatians 4:19. He explains that the true battle of the Christian faith is not about systems, doctrines, or forms of worship, but rather about the fullness of Christ's presence in believers and the Church. Sparks contrasts the immaturity of spiritual children with the responsibility and understanding of mature sons, highlighting that the Holy Spirit's role is to facilitate this growth. He urges believers to reflect on their spiritual suffering and ensure it is for the sake of Christ's formation within them, rather than for personal grievances or issues. Ultimately, the sermon calls for a focus on the spiritual maturity that comes from allowing Christ to be fully realized in our lives.