In “Sealed! The Spirit at Work in Us,” John of Black Hills Church of Christ turns to Ephesians 1 to show that the Holy Spirit’s seal is God’s own guarantee of our salvation. Contrasting a common “in-and-out” view that treats security as a matter of our latest performance with the Bible’s emphasis on God’s finished work, the message traces Christ’s once-for-all sacrifice (Hebrews 9–10), the declaration of no condemnation for those in Christ (Romans 8:1), and the ongoing reality of forgiveness for those who walk in the light (1 John 1). Believers are not bouncing between saved and lost; they are already sealed, and the Spirit’s presence is the down payment that their redemption is sure. The sermon invites anyone not yet in Christ to respond, while calling those who are to rest in what God has already done and to live in light of that security.