When it comes to believing (and presenting) the Gospel, it is very important to be as precise as possible. Distinctions must be made and maintained, even if some think this is a process of hair-splitting. For example, it is one thing to believe that Christ died for my sins, but it is another to believe the Christ who died for my sins. The first is an action Christ performed, the second is a person, Jesus Christ. Here is how J.I. Packer makes this important distinction:
We must not present the saving work of Christ apart from His Person. Evangelistic preachers and personal workers have sometimes been known to make this mistake. In their concern to focus attention on the atoning death of Christ as the sole sufficient ground on which sinners may be accepted with God, they have expounded the summons to saving faith in these terms: “Believe that Christ died for your sins.” The effect of this exposition is to represent the saving work of Christ in the past, dissociated from His Person in the present, as the whole object of our trust. But it is not biblical thus to isolate the work from the Worker.
Nowhere in the New Testament is the call to believe expressed in such terms. What the New Testament calls for is faith in (en) or into (eis) or upon (epi) Christ Himself—the placing of our trust in the living Savior Who died for sins. The object of saving faith is thus not, strictly speaking, the atonement, but the Lord Jesus Christ, Who made atonement. We must not, in presenting the gospel, isolate the cross and its benefits from the Christ Whose cross it was. For the persons to whom the benefits of Christ’s death belong are just those who trust His Person and believe, not upon His saving death simply, but upon Him, the living Savior.
“Believe on the Lord Jesus Christ, and thou shalt be saved,” said Paul (Act 16:31). “Come unto me…and I will give you rest,” said our Lord (Mat 11:28).
From Packer’s What Is the Gospel Message.