For by the grace we are saved through the faith, and this [faith] is not out from you; it is a gift from God, not out from works, in order that no one should boast (Ephesians 2:8–9)
Grace is God’s attitude whereby He gives a benefit without consideration of merit. Faith is taking God at His Word—it is the foundation upon which hope stands (Hebrews 11:1). Salvation is offered by believing that Christ died on behalf of our sins and was raised three days later according to the Scriptures (1 Corinthians 15:3–4). This is the only message with the inherent ability to save (Romans 1:16).
Since salvation is offered based on God’s desire to provide the benefit of salvation, the only way to obtain it is through faith in the facts of the gospel. Since faith must have a promise—for without a promise, there is no hope, and without faith, hope has no expectation—this is not merely believing God exists. Faith is taking God at His Word and, therefore, requires a promise in which to place eager expectation for its fulfillment.