The Gospel is God's announcement that He has provided forgiveness of our rebellion against Him, a new relationship with Himself, and life-eternal through the life, death and resurrection of His one and only Son, the Lord Jesus Christ. Through the Gospel God calls us to respond by turning away from our rebellion, surrendering our lives to Him and placing our trust in Christ alone for salvation.
Jesus lived a perfect life in fulfillment of God's Law, then died an atoning death to satisfy the justice of God for us who have broken His law. His bodily resurrection from the dead three days later demonstrated the effectiveness of His sacrifice and his power over death.
Now through faith in Jesus his perfect life is credited to us, his atoning death is counted as our payment to God's justice and we can be forgiven of our sins, adopted into God's family and given a new heart to serve God.
“Jesus said to her, “I am the resurrection and the life. Whoever believes in me, though he die, yet shall he live, and everyone who lives and believes in me shall never die. Do you believe this?””
(John 11:25–26 ESV)