We must be born again, but where do we get such new birth from? As with everything else in salvation, we get it through Christ. Let me put it this way...
On Easter Sunday, the Bible speaks of a significant newness regarding Jesus.
Romans 1:4 says “through the Spirit of holiness [Jesus] was declared with power to be the Son of God.”
Jesus was already the Son of God, but Easter “declared” Him to be so with power.
Colossians 1:18 says Jesus is “Firstborn from the dead.”
Jesus was already Firstborn (Colossians 1:15) but He was not Firstborn from among the dead until Easter morning. This was very much a new birth for Jesus.
1 Timothy 3:15 says Jesus was “justified in the Spirit” (referring almost certainly to His resurrection).
Again, He was always righteous – indeed He is the Righteous One. Yet He is vindicated to be so when He rises from the dead.
1 Peter 3:18 says Jesus was “put to death in the flesh, but made alive in the Spirit.”
Once more, Jesus is the Living One – indeed He is the Author of life. But His resurrection marks a movement from flesh-life to Spirit-life. In other words, there is a movement from the life He took on in incarnation to the glorified humanity He receives in resurrection.
1 Corinthians 15 is a sustained meditation on this resurrection reality. First comes the natural body then the spiritual (v44). The fact that we pass from natural to spiritual is because Jesus is the Firstfruits (v20-23). He is the Pioneer of this movement from flesh-life to Spirit-life.
In this sense I would say that Jesus pioneers the new birth. He passes through death and judgement (a death and judgement which He did not deserve). He comes out the other side in glorified, resurrection life. And the new life He offers to us is a participation in His new life. Where do we get our new birth from? We get it from Jesus.
Now this can sound really odd to people. Jesus gets a new birth? What?
I think part of the misunderstanding on this issue involves a misconception about salvation. At a popular level we understand salvation fairly Christlessly. We imagine that getting saved means "getting zapped" by God. It's something that lands on sinners by the power of the Spirit and brings them to God. And Jesus is not really a part of the equation. Therefore since Jesus isn't a sinner in need of 'getting saved' (and He's not!) we see no role for Jesus. This Spirit-centric view of salvation leaves Jesus out of regeneration.
But salvation centres on Jesus. He works it. Through His doing and dying we are saved. And the Spirit seals us into Him. Thus salvation is located in Christ. If we have eternal life, it's a participation in His eternal life. If we have righteousness, it's a participation in His righteousness. If we have a new birth, it's a participation in His new birth.
Another problem in our understanding is conceiving of the "new birth" much more narrowly than the Bible. Remember that heaven and earth will be made new (e.g. Isaiah 65:17). In Jesus’ words, there will be a “regeneration” of all things (Matthew 19:28). It is not simply sinners who need the new birth. New birth is required for the whole old order. And only Jesus can bring it to us.
Here's how He does it. Jesus enters into the world and takes on our flesh. He takes responsibility for this old world by standing at its Head. He takes the old world and the old man down into death. But God raises Him by the Spirit to newness of life. As Firstborn from among the dead He offers us a share in His Firstborn-ness (if I can put it like that). As Firstfruits He offers to graft us in to His fruitful new life. As Risen One, He offers us new birth into His living hope (1 Peter 1:3).
That’s the sense in which Jesus pioneered the new birth.