1 John5:8

I have already said that water was necessary for cleansing and the blood was necessary for atonement. Cleansing and atonement are tied closely to the major building blocks of the Jewish understanding of the universe which were the conditions of common and clean, uncommon (holy) and clean, common and unclean. Cleansing and atonement provided mobility from a less desirable state (common and unclean) to the most desirable state (clean and holy).

But here the Holy Spirit, and His connection to our own spirits, is added into the mix. This introduced another huge building block of the Jewish understanding of the universe, i.e. that everything is made up of a body (a physical reality), a soul and/or a spirit, or some combination of those three. Humans have all three aspects, a body, a soul and a spirit, and, ideally, all three of these should function in full agreement with each other. But for many people, even many believers, there is no agreement between their three major building blocks; the body is emphasized over the soul, and the spirit is suppressed rather than developed.

The verse above is part of a set of proofs that Jesus is God in the flesh, and the long-awaited Messiah. Jesus is shown to be God by embodying in Himself all the major themes of the Torah. God was the giver of the Torah, so only God can fulfill the Torah perfectly. Jesus has provided for our cleansing and atonement, which provide movement from common and unclean to clean and holy, and He has facilitated unity between the body, soul and spirit. Furthermore, He was the fulfillment of all the Old Testament sacrifices. Since Jesus fulfilled and completed all of the Torah, He must be God in human form!