T. Austin-Sparks emphasizes the profound nature of 'so great salvation' as described in Hebrews 2:3, exploring its comprehensive aspects such as substitution, representation, redemption, justification, reconciliation, regeneration, sonship, sanctification, and glorification. He explains that humanity's inability to meet divine requirements necessitates a substitute, Jesus Christ, who takes on our sins and offers us redemption and justification. The sermon highlights the transformative journey from being alienated from God to becoming reconciled and sanctified, ultimately leading to glorification. Sparks warns against neglecting this great salvation, underscoring the importance of recognizing and embracing the fullness of what Christ has accomplished for us. The message calls believers to grow in their understanding and experience of their salvation, moving towards maturity in Christ.