Jesus tells Nicodemus, “Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God” (Jn 3:5). What does this mean?
The reading that’s most attractive to me sees “of water and of the Spirit” as a shorthand reference to two closely linked passages in Ezekiel 36-37, both concerning the LORD’s redemption of Israel from her bondage in exile. (I’ve already written here about their presence in Mark.) In Ezekiel 36:22-26, the LORD depicts this saving action both in terms of washing and in terms of the Spirit’s indwelling: “I will take you from among the heathen, and gather you out of all countries, and will bring you into your own land. Then will I sprinkle clean water upon you, and ye shall be clean: from all your filthiness, and from all your idols, will I cleanse you. A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.” Then, in Ezekiel 37:1-14, we hear of the LORD’s resurrection of exiled Israel from their graves by the power of the Spirit: “I will open your graves, and cause you to come up out of your graves, and bring you into the land of Israel…And shall put my spirit in you, and ye shall live, and I shall place you in your own land: then shall ye know that I the LORD have spoken it, and performed it, saith the LORD” (37:12, 14). Israel will be reborn by water and the Spirit, that is, by baptism and by the Spirit’s indwelling (sacramentally realized in the chrism applied after baptism).
The fly in the ointment for that reading is the very next verse in John, which might suggest a different approach: “Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit” (Jn 3:5-6). In v. 5, a birth from water is paired with a birth from the Spirit; in v. 6, a birth from flesh is juxtaposed with a birth from the Spirit. Might that not suggest that birth from water is identical to the birth from the flesh, in the sense that we are born from water of our mothers’ wombs? That would make baptism irrelevant to the logic of salvation as it’s depicted in John 3.
Either reading is grammatically possible; we’d need to think more about John’s use of water and Spirit imagery to decide which is most obviously recommended by the overall context of the Gospel (I’ll circle back around to that eventually). But in canonical context, the former reading, with a high view of baptism, seems to me to be clearly the correct one. “As many of you as have been baptized into Christ have put on Christ” (Gal 3:27). “So many of us as were baptized into Jesus Christ were baptized into his death. Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life” (Rom 6:3-4). “Baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ” (1 Pet 3:21).