How do we know the doctrine of eternal life is true?

John writes in 1 John 2:25 that the promise of eternal life is a gift from God. This promise is not dependent on human actions but is irrevocable and grounded in the nature of God and His covenant of grace. The assurance comes from believing that Jesus is the Christ, the Son of God. Throughout the New Testament, we find reiterated guarantees of eternal life for those who place their faith in Christ, providing believers with unwavering confidence in God's promises. The culmination of this doctrine assures us that our faith rests firmly on the unchanging character of God, who fulfills His commitments to His elect.