Here is the commentaries on this verse of some highly respected theologians.
As you can see, even among Conservative Evangelical Theologians, they cannot seem to quite agree on what it means. I still LEAN towards natural birth because of the OBVIOUS comparison between Natural Birth ans Spiritual Birth in verse six. This was a continuous train of thought in a conversation, WITHOUT CHAPTER NUMBERS AND VERSE NUMBERS. I seems illogical to change the subject from one sentence to the next, therefore I take verse six to be HIS OWN EXPLANATION OF WHAT HE MEANT IN VERSE 5.
How about we ask HIM personally when we get to heaven.
As you can see, even among Conservative Evangelical Theologians, they cannot seem to quite agree on what it means. I still LEAN towards natural birth because of the OBVIOUS comparison between Natural Birth ans Spiritual Birth in verse six. This was a continuous train of thought in a conversation, WITHOUT CHAPTER NUMBERS AND VERSE NUMBERS. I seems illogical to change the subject from one sentence to the next, therefore I take verse six to be HIS OWN EXPLANATION OF WHAT HE MEANT IN VERSE 5.
How about we ask HIM personally when we get to heaven.
Here is what St John Chrysostom of the forth century says of John 3:5 in his homilie..
"That the need of water is absolute and indispensable, you may learn in this way. On one occasion, when the Spirit had flown down before the water was applied, the Apostle did not stay at this point, but, as though the water were necessary and not superfluous, observe what he says; Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we? Acts 10:47What then is the use of the water? This too I will tell you hereafter, when I reveal to you the hidden mystery. There are also other points of mystical teaching connected with the matter, but for the present I will mention to you one out of many. What is this one? In Baptism are fulfilled the pledges of our covenant with God; burial and death, resurrection and life; and these take place all at once. For when we immerse our heads in the water, the old man is buried as in a tomb below, and wholly sunk forever; then as we raise them again, the new man rises in its stead. As it is easy for us to dip and to lift our heads again, so it is easy for God to bury the old man, and to show forth the new. And this is done thrice, that you may learn that the power of the Father, the Son, and the Holy Ghost fulfills all this. To show that what we say is no conjecture, hear Paul saying, We are buried with Him by Baptism into death: and again, Our old man is crucified with Him: and again, We have been planted together in the likeness of His death. Romans 6:4-6 And not only is Baptism called a cross, but the cross is called Baptism. With the Baptism, says Christ, that I am baptized withal shall you be baptized Mark 10:39: and, I have a Baptism to be baptized with Luke 12:50 (which you know not); for as we easily dip and lift our heads again, so He also easily died and rose again when He willed or rather much more easily, though He tarried the three days for the dispensation of a certain mystery."
Another by Cyril of Jerusalem. Cetechetical Lectures #3.
" For since man is of twofold nature, soul and body, the purification also is twofold, the one incorporeal for the incorporeal part, and the other bodily for the body: the water cleanses the body, and the Spirit seals the soul; that we may draw near unto God, having our heart sprinkled by the Spirit, and our body washed with pure water. Hebrews 10:22 When going down, therefore, into the water, think not of the bare element, but look for salvation by the power of the Holy Ghost: for without both you can not possibly be made perfect. It is not I that say this, but the Lord Jesus Christ, who has the power in this matter: for He says, Unless a man be born anew (and He adds the words) of water and of the Spirit, he cannot enter into the kingdom of God. John 3:3 Neither does he that is baptized with water, but not found worthy of the Spirit, receive the grace in perfection; nor if a man be virtuous in his deeds, but receive not the seal by water, shall he enter into the kingdom of heaven. A bold saying, but not mine, for it is Jesus who has declared it: and here is the proof of the statement from Holy Scripture. Cornelius was a just man, who was honoured with a vision of Angels, and had set up his prayers and almsdeeds as a good memorial before God in heaven. Peter came, and the Spirit was poured out upon them that believed, and they spoke with other tongues, and prophesied: and after the grace of the Spirit the Scripture says that Peter commanded them to be baptized in the name of Jesus Christ Acts 10:48; in order that, the soul having been born again by faith , the body also might by the water partake of the grace."
And St Ambrose - On the Mysteries, chp 4
"Therefore read that the three witnesses in baptism, the water, the blood, and the Spirit, 1 John 5:7 are one, for if you take away one of these, the Sacrament of Baptism does not exist. For what is water without the cross of Christ? A common element, without any sacramental effect. Nor, again, is there the Sacrament of Regeneration without water: For except a man be born again of water and of the Spirit, he cannot enter into the kingdom of God. John 3:5 Now, even the catechumen believes in the cross of the Lord Jesus, wherewith he too is signed; but unless he be baptized in the Name of the Father, and of the Son, and of the Holy Spirit, he cannot receive remission of sins nor gain the gift of spiritual grace."
I don't need to wait until I get to heaven to know what scripture meant from the beginning. The Holy Spirit gave the Gospel ONCE, which includes its meaning, and has preserved Christ's Gospel within His Body.