John Piper has a new book, Finally Alive on various aspects of regeneration. Piper has made some startling comments (at least to me) on the relationship between faith and regeneration. Why are they startling? Because knowing Piper’s strong Calvinism theology, he has made some strong statements regarding the necessity of faith in regeneration.
Here is how John puts them together in his First Epistle: “For whatever is born of God overcomes the world. And this is the victory that has overcome the world—our faith” (1 John 5:4). “Born of God” is the key to victory. “Faith” is the key to victory. Both are true because faith is the way we experience being born of God. Being born of God always brings faith with it. The life given in the new birth is the life of faith. The two are never separate.
Or consider how John says it in 1 John 5:11-12: “This is the testimony, that God gave us eternal life, and this life is in his Son. Whoever has the Son has life, whoever does not have the Son of God does not have life.” Therefore, when Jesus says, “It is the Spirit who gives life” (John 6:63), and, “You must be born of the Spirit” (John 3:5, 8), and, “Believing you may have life” (John 20:31), he means: In the new birth, the Holy Spirit supernaturally gives us new spiritual life by connecting us with Jesus Christ through faith. For Jesus is life.
Therefore, when answering the question What happens in the new birth? never separate these two sayings of Jesus in John 3: “Unless one is born again he cannot see the kingdom of God” (v. 3), and, “Whoever believes in the Son has eternal life” (v. 36). What happens in the new birth is the creation of life in union with Christ. And part of how God does that is by the creation of faith which is how we experience our union with Christ.
Immediately preceding this section, Piper wrote the following:
And from our side, the way we experience this is that faith in Jesus is awakened in our hearts. Spiritual life and faith in Jesus come into being together. The new life makes the faith possible, and since spiritual life always awakens faith and expresses itself in faith, there is no life without faith in Jesus. Therefore, we should never separate the new birth from faith in Jesus. From God’s side, we are united to Christ in the new birth. That’s what the Holy Spirit does. From our side, we experience this union by faith in Jesus.
To me there is not really anyway to get around the fact that Piper is saying faith and regeneration are simultaneous. God is the initiator, Yes! Man responds, Yes! But if there is no separation of time, then by definition they are simultaneous. I agree, or I should say Piper finally agrees with me!
You might think I would say that we have no involvement in it [regeneration], because we are spiritually dead. But the dead are very much involved in their resurrection—after all, they rise! Here is an example of what I mean. When Jesus stood before the grave of Lazarus who had been dead four days, Lazarus had no part in imparting his new life. He was dead. Jesus, not Lazarus, created the new life.
In John 11:43, Jesus says to the dead Lazarus, “Lazarus, come out.” And the next verse says, “The man who had died came out.” So Lazarus takes part in this resurrection. He comes out. Christ causes it. Lazarus does it. He is the one who rises from the dead! Christ brings about the resurrection. Lazarus acts out the resurrection. The instant Christ commands Lazarus to rise, Lazarus does the rising. The instant God gives new life, we do the living. The instant the Spirit produces faith, we do the believing.
So that’s why I am asking two questions, and not just one question, when I ask How are we born again? I am asking: What does God do in our new birth? How are we born again from God’s side? And I am asking: What do we do in our new birth? How are we born again from our side? 
Consider verses 23-25: “You have been born again, not of perishable seed but of imperishable, through the living and abiding word of God.” Notice: The new birth happens through the word of God. Verse 25 says that this word of God “is the good news that was preached to you.” 
And when the Spirit connects you to me by faith, you experience new birth.
The answer continues like this: Your act of believing and God’s act of begetting are simultaneous. He does the begetting and you do the believing at the same instant. And—this is very important—his doing is the decisive cause of your doing. His begetting is the decisive cause of your believing.
(Eph 1:13 ESV) “In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit.”
(Col 1:5 ESV) “because of the hope laid up for you in heaven. Of this you have heard before in the word of the truth, the gospel.”
It is our new birth. It involves our believing in the gospel of Jesus Christ. That’s why I say that my new birth does not take place without me believing. In believing we are acting out the new birth, we are breathing in the new life.
What then does this mean for us?…
1. It means that we must believe in order to be saved. “Believe in the Lord Jesus Christ and be saved” (Acts 16:31). The new birth does not take the place of faith; the new birth involves faith. The new birth is the birth of faith.
 Piper, John. Finally Alive. (Fearn: Christian Focus), 2009), 33.
 Ibid., 32.
 Ibid., 79.
 Ibid., 83.
 Ibid., 92.
 Ibid., 102.
 Ibid., 104, footnote 14.
 Ibid., 105.
 Ibid., 107.