What does the Bible say about the gospel call to believe in Christ?

The gospel's call is to believe in the sufficiency of Christ's atonement for salvation. Romans 1-3 emphasizes that no one can be justified by their own works, and it lays the groundwork for the necessity of faith in Christ. This means that the first act of faith called for by the gospel is recognizing that salvation cannot be found in ourselves, but rather in the promised Redeemer, Jesus Christ, who is the only name under heaven by which we can be saved (Acts 4:12). It is through God's gospel that we are invited to trust in Him alone, as the true object of our faith, and to rest in His completed work for our justification.