http://biblos.com/john/3-5.htm
http://www.biblegateway.com/passage/?search=John+3&version=NIV
John 3:3 In reply Jesus declared, “I tell you the truth, no one can see the kingdom of God unless he is born again.”
4”How can a man be born when he is old?” Nicodemus asked. “Surely he cannot enter a second time into his mother’s womb to be born!”
5Jesus answered, “I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit. 6Flesh gives birth to flesh, but the Spirit gives birth to spirit. 7You should not be surprised at my saying, ‘You must be born again.’ 8The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit.”
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Being born of water is the physical birth. Verse six lays to rest the contention that eating the Eucharist does anything spiritually.
Just like Matt 16:18 establishes Peter as the rock on which Christ builds his Church.
John 6:53-58
53 Jesus said to them, “Amen, amen, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you.
54 Whoever eats 19 my flesh and drinks my blood has eternal life, and I will raise him on the last day.
55 For my flesh is true food, and my blood is true drink.
56 Whoever eats my flesh and drinks my blood remains in me and I in him.
57 Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me.
58 This is the bread that came down from heaven. Unlike your ancestors who ate and still died, whoever eats this bread will live forever.”
Christ seems to disagree with your assertion about the Eucharist.