The Holy Spirit plays a key role in regeneration and the indwelling and sealing of believers. Regeneration involves being born again by the Spirit and imparting eternal life, changing one from spiritual death to life. All believers are universally indwelled by the Spirit at salvation, seen as an anointing and sealing by God, not dependent on human worthiness. Indwelling sets believers apart for God and contrasts with other ministries like filling, though it occurs simultaneously with regeneration. Sealing by the Spirit provides security and assurance of salvation.