Jethro said -
..and flesh gives birth to flesh, and Paul explains what that means. And it does not mean natural child birth. It means being birthed a natural man of flesh, not a spiritual one, through an old covenant style obedience (the effort of self alone) to the requirements of God. It's impossible to say the Bible does not teach this truth about obedience alone. And Jesus describing the birth he is talking about--the birth by water--which can not usher a person into the kingdom of God fits exactly in line with what Paul is teaching in Galatians 4 about the birth of the person, the man of works, who will not be ushered into the kingdom of God.
Flesh gives birth to flesh is a reference to child birth of the natural body.
Flesh is a reference here to the natural body.
Paul uses the term flesh to refer to the natural body, and how the desires of the natural earthly body, has lustful cravings that are opposed to the Spirit.
19
Now the works of the flesh are evident, which are: adultery, fornication, uncleanness, lewdness, 20 idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, 21 envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God.
Galatians 5:19
This sinful nature still resides in the natural body and is opposed to the desires of the Spirit, that indwells the believer.
Paul encourages believers not to follow, or give in to these desires that remain in the physical body of a believer, though they have been born again.
The flesh is a reference to the physical body that is empowered by the sinful nature within.
The born again believer has been regenerated within, yet still struggles with the desires of the physical body.
Flesh is a reference to the physical body.
Flesh gives birth to flesh, is a reference to birth. This birth is of the natural earthly body.
Your interpretation of the words of jesus in John 3, are diametrically opposed to the new testament teachings.
Your interpretation states this -
[Born of water] repentance gives birth to a fleshly, non spiritual person.
This is what you are advocating, and don't seem to realize it.
JLB