Pastor Heyer uses King David's sin with Bathsheba to illustrate that, while sin affects those around us, it is fundamentally an offense against God. He explores how David's actions broke both tables of the Law, the commandments concerning God and those concerning neighbors. The sermon emphasizes that God's justice for sin is death, but his mercy is shown through Jesus Christ, who took humanity's place and punishment. Ultimately, true repentance involves recognizing sin, understanding God's just and merciful response, and desiring to live according to God's commands daily.