If salvation wasn’t complete already, it could not be presented as a gift. Anything called “gift” was first acquired by someone before it was presented as gift..The competeness of God’s salvation on the cross was fully achieved by God through Christ’s sacrificial death and it didn’t need man’s faith to make it more complete.
The unbelief of men prior to the cross did not stop it from becoming complete on the cross. The same way the unbelief of men today does not or cannot interrupt its completeness.
Salvation remains complete with or without anyone’s faith. When men are asked to believe in Jesus Christ, it is not because their faith will give God any advantage or add anything to what Christ has done, rather, it is for their own advantage.
The one who believes in Christ or accepts his gift of eternal life through faith in Christ benefits from his new relationship with Christ. The benefit is not just one thing but many things. It is to every man’s advantage that they believe that Jesus Christ died for their sins.
If man could save himself, then Jesus death on the cross is the most useless thing that has ever happened in human history.
But since a sinner cannot save himself because he is helpless, God sent his only unique Son to come to the world, and through his death, offer salvation as a free gift to all men without any discrimination………For what does the scripture say besides Christ?
“Nor is there salvation in any other, for there is no other name under heaven given among men by which we must be saved.” Acts 4:12