James Jordan recently pointed out in private conversation how appropriate it is, in John’s Gospel, that Nicodemus is present both to ask Jesus about being born again, and to see Jesus re-enter the womb of the mother.
Nicodemus rhetorically asks, “How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?” Then he gets to witness Jesus’ answer by being present for Jesus’ burial: “Now in the place where he was crucified there was a garden, and in the garden a new tomb in which no one had yet been laid” (compare Genesis 24.16a: “The young woman was very attractive in appearance, a maiden whom no man had known”).
New birth as metaphor for resurrection should not surprise us. It correlates to Adam’s first birth from the earth by the Spirit (thus, Paul’s direct comparison between Adam’s creation and Christ’s resurrection). In fact, evidence for this idea fills the New Testament (see here or here for some further evidence).