At one point in the Gospel of John, the people directly asked Jesus what they must do to please God: “’What must we do to do the works God requires?’ Jesus Answered, ‘The work of God is this: to believe in the one he has sent’” (6:28-29).

• True belief is not a probationary test drive; it is not armchair speculation or a passive religious gamble concerning the after life. Saving belief is a belief that lasts.
• True belief is a reliance on Jesus, as well as a belief that Jesus is telling the truth about Himself. True belief does not simply mean believing Jesus, that is, believing that he is telling the truth and is not speaking lies. Rather, the work God requires is this: to believe in the one he has sent. Or as Jesus says elsewhere, “He who believes in me will live, even though he dies; and whoever lives and believes in me will never die” (11:25-26). To believe, then, is to rely completely on his person and to trust totally what he teaches about himself. True believers see Jesus for who he says he is, and they rely on him.
• True belief manifests itself in obedience. Jesus tells us, “whoever has my commandments and keeps them, he it is who loves me. And he who loves me will be loved by my Father, and I will love him and manifest myself to him” (14:21).

We are to believe the facts about Jesus – that he came from God, lived, died, and rose again. And we are to believe in the person and work of Jesus – that we can rely on his love and sacrifice for us on the cross. But when we receive these things through God’s work in our hearts and lives, we will believe in him with persevering love and obedience.”

Mark Dever, The Message of the New Testament (Wheaton, IL: Crossway, 2005).