“Jesus answered, “Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. “That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. “Do not marvel that I said to you, ‘You must be born again”, John 3:5-7.

It appears that Jesus was differentiating the two births. There are 2 caveats according to Him, viz.,
1. Being born of the flesh is flesh
2. Being born of the spirit is spirit.

It seems that these requisites also refer to 2 attributes, viz., “timing”, i.e. when a person is actually born, and also to “body-composition”, flesh or spirit.
And, with that understanding, we can now analyze what Jesus meant.

Can anyone really assume “born” refers to an adult coming out of “water baptism”? An adult has already been born flesh and as such, he/she goes for water baptism; goes in as “flesh” and comes out still “flesh”. Most likely not. Moreover, a fetus has not yet been born, and covered in “amniotic fluid”(water). When “born” the newborn was “born of water” and certainly is “flesh”. At the “timing” of birth, the person is “flesh”.

On the other hand, the timing of “being born of the spirit” is like being “firstborn from the dead”. The only example of this is what happened to man-Jesus, the “first of the firstborn from the dead”(Col.1:18). No one can dispute that at resurrection (firstborn from the dead) he was/is “spirit-composed” with the ability to be seen, in the same way that angelic-spirits can show themselves to humans (Gen. 18; Matt. 28:1; Lu.24:,10-24; John 20:19-22; 1 Corinthians 15:6-9). And, we will follow that path of becoming “born of the spirit”, also at resurrection of the dead.

In short, as Jesus said, “most assuredly”, one has to born “flesh” first before being “born of the Spirit”. During growth and development in utero, the fetus is covered with water/amniotic fluid before being “born”. Likewise, we need to be “all covered” (infused) with the Holy Spirit in our current flesh composition for “sealing, guidance, protection, maturing, i.e., “growth & development” as in,
Ezekiel 36:25-27, “25 Then I will sprinkle clean water on you, and you shall be clean; I will cleanse you from all your filthiness and from all your idols. 26 I will give you a new heart and put a new spirit within you; I will take the heart of stone out of your flesh and give you a heart of flesh. 27 I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them”.

All of these processes to be “one” with Jesus, our “forerunner”(Heb. 6:20). Then, this flesh will change in a “twinkling of an eye” from flesh/mortal to spirit/immortal
(I Cor. 15:52).