Not only did Jesus need to be the right Person and do the right works for us to be saved, but He also had to make the right promise. Without the promise of everlasting life, no one could be saved.
Why is the promise of Christ essential for salvation? Because the promise of everlasting life is one of two things that He said that we must believe to be born again (John 4:10).
He stated the promise in verses like John 3:16; 4:1-14; 5:24; 6:47; 11:26; Rev 22:17.
In the NT this promise is called “the promise of life” (2 Tim 1:1; see also Gal 3:21; Titus 1:2) or “the word of life” (Acts 5:20; Phil 2:16; see also 1 John 1:1).
The promise is found in the OT as well, starting in Gen 3:15 and continuing in Gen 15:6. The Lord Jesus said the OT declared that those who believe in Him have everlasting life (John 5:39-40). Hebrews 11 gives many examples of OT people who believed in Jesus for their eternal destiny. See also John 8:56.
Some have suggested that one need not believe the promise of Christ in order to be born again. They suggest that faith in Christ’s Person and work is sufficient.
In his book, The Future of Justification: A Response to N. T. Wright, John Piper has a section that asks the question, “We Are Not Justified by Belief in Justification?”i He quotes Wright as saying, “We are not justified by faith by believing in justification by faith. We are justified by faith by believing the gospel itself—in other words, that Jesus is Lord and that God raised him from the dead.”ii Piper continues,
This sounds right. Of course, we are not saved by doctrine. We are saved by Christ. But it is misleading because it leaves the meaning of “believing in the gospel” undefined. Believing in the gospel for what? Prosperity? Healing? A new job?…we will have to announce why this death and resurrection are good news for them (italics his).iii
If someone does not believe in Jesus for the promise of an irrevocable justification/salvation, then he has not yet believed the message of John 3:16 or a host of other passages in the Bible. The Lord was clear that whoever believes in Him will never perish, will never die spiritually, will never be cast out, will never be plucked out of His hand, and will never hunger or thirst for everlasting life.
The Lord told the woman at the well that she needed to believe in two things: the gift of God and the Giver of the gift (John 4:10). He went on to say that the gift of God is everlasting life that cannot be lost (John 4:14) and that He, the Giver, is the Messiah (John 4:25-26). If one does not believe in the gift of God that is promised by the Lord Jesus Christ, then he has not yet drunk of the living water.
Hypothetically, the Lord might not have evangelized anyone. He could have delegated to the apostles and subsequent believers the preaching of the promise of everlasting life. But part of the Father’s assignment for Him was that He preach the promise of everlasting life (John 5:24; 6:35-40). He served as the example of what He wanted His followers to proclaim.
The apostles are not the head of the church; the Lord Jesus is. As the head, He is everlasting life (John 14:6; 1 John 5:20); He perfectly lived out that life; He gave us the transferable promise of life that all believers are to proclaim; He died on the cross for our sins; and He rose bodily from the dead.
The promise of Christ is the bullseye. That is what turns an unbeliever into a believer. When a person comes to believe that whoever believes in Jesus has everlasting life, then he “has passed from death into life” (John 5:24).
Don’t forget the promise of Christ.
i John Piper, The Future of Justification (Wheaton, IL: Crossway, 2007), p. 20.