If you deny the sacramental readin of John 3:5, what’s left? You’d have to argue that “water” means some Old Testament symbol, like the water from the rock or the water of the Red Sea. But that wouldn’t make sense in the sentance: Is Jesus saying we must be born of the Red Sea and the Holy Spirit?
1. This commenter, in asking his question, altogether ignores Steve’s initial presentation. He pretends that the anachronistic and acontextual properties of the sacramental reading are non-existent. In asking, “What’s left,” he expects one to accept an improbable reading on the basis that it is, supposedly, the only reading available. The fact that such a reading is wholly out of synchronization with the rest of John’s themes seems to matter little to this commenter.
2. For years, I ignorantly assumed that the birth “of water” referred to the amniotic fluid that flows in the process of birth (”water breaks”). But this type of reading is almost as anachronistic as the sacramental reading, for there is no evidence in any early manuscript that birth was referred to in this manner.
3. Furthermore, as was pointed out in the comments section, the Greek text does not refer to two births, but one. It does not distinguish between a natural birth and a spiritual birth. Rather, both births are referred to by the same preposition (rather than “of water and of spirit,” it is simply “of water and spirit”: εξ υδατος και πνευματος). The spiritual birth is the water birth.
4. Jesus, rather than alluding to something about which Nicodemus would have no clue (baptismal regeneration), he refers to something which Nicodemus would have easily understood:
Ezekiel 36:25-27 I will sprinkle clean water on you, and you shall be clean from all your uncleannesses, and from all your idols I will cleanse you. And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules.
One must be regenerated to enter the Kingdom of God, and this regeneration involves the dual work of both being cleansed of sin and receiving the Spirit. In order to enter the Kingdom, one must not only be free from his sins, but he must possess a heart of flesh and the Spirit of God that is received in regeneration.