Nicodemus is the quintessential religious person. This kind of person has a mind towards the things of God, an understanding of theology, he gravitates towards morality, and even has the potential to be well-respected in society precisely for his religion. Here Nicodemus is "a leader of the Jews" (Jn. 3:3). He is "the" teacher of Israel (Jn. 3:10). He does what needs doing, and has influence doing it - there is no evidence of malice or insincerity in him.
And that is his very problem (John 3). All this does not indicate favor with God but a love for self - he does not know Jesus nor salvation. For this all he gets from Jesus is rebuke, no commendation (v3, v7, v10). In Nicodemus' conversation with Jesus, What drives his thinking is human ability, where Jesus' corrective is to describe the need for supernatural intervention in his life. He begins with genuine praise for Jesus' works, which Jesus rebuts with his real need - "unless you are born from above, you cannot comprehend the kingdom of God" (v3)
- from the outset Jesus pinpoints the problem as showing his human merit as garbage, because it does not help "seeing" or "comprehending" the kingdom of God. Obviously, Nicodemus' logical, intellectual and theological prowess could not help him in this comprehension.
- "birth" itself in a purely natural sense is one of helpless inaction - a baby has no will in the matter.
It is there that Jesus explains further:
- To enter the kingdom, one must have a spiritual nature (v5)
- Natural birth is insufficient (v6)
- This transformation, spiritual birth is not visible but it is observable, but it is ultimately the prerogative of the Spirit, who "blows where He will" (v7-8)
Those who reassure themselves of the love of God by their morality, by their piety, by their theology, by their any deed, they must see this: John 3:16 - God's love precedes your deeds OR your faith. His already existing perfect love for the world is why he "gave his only Son". Nothing about your salvation merits his love, it is all a result of his love. You can know God because He loved you, and the only way to know him is to cast yourself on his mercy, like a dying, snake-bitten desert nomad, lost and hopeless. A disciple of Jesus works not to win love, but works as a result of winning love, by the life-giving Spirit of Christ.