John Gill expounds on the eternal acts of God, particularly focusing on adoption and justification. He emphasizes that both acts are rooted in God's eternal will, with adoption being God's choice to make certain individuals His children, and justification being God's declaration of righteousness towards the elect. Gill clarifies that these acts are not contingent upon human actions or faith but are established in God's sovereign grace from eternity. He argues that justification is an internal act of God that precedes faith and is based on Christ's righteousness, which was secured for the elect before the foundation of the world. The sermon highlights the profound nature of God's grace in adopting and justifying unworthy sinners.