My friend Peter Leithart tags to an argument by Alan Kerr on the Spirit in John 3. Kerr’s argument, in sum, is that in the gospel of John, the Spirit is not given until later in the gospel (John 20:22). This means, on this reading, that whatever Jesus was talking about with Nicodemus could only be realized after the resurrection. If true, as Peter notes, this has ramifications for John 3:5 as a text on regeneration.
But the key here is “if true.” I find Kerr’s suggestion unconvincing for several reasons. First, Jesus expected Nicodemus to know what He was talking about, simply by virtue of being a teacher in Israel (John 3:9). Second, how could Nicodemus be expected to know this? One of the first places I would go to would be Eze. 37 — Israel was a valley of dry bones and needed to be , reborn, and this was going to be done by the breath of God (Eze. 37:4-5). The regeneration of all Israel was going to have to wait until Acts 2, but all individual regenerations up to that time were proleptic after a fashion — just as Jesus breathing on the disciples in John 20 was. And third, it seems like such an argument like that would prove too much. In other words, Jesus is contrasting those born of the flesh and those born of the Spirit, each according to their kind. Do we really want to lock up all Old Testament believers in that birth of the flesh alone? I know that nobody does, but this argument would seem to require it.