Nicodemus is following this conversation, but many people today are not.
Jesus says he must be born again.
Nicodemus assumes that by saying 'born again' Jesus is talking about a physical birth or one of the 6 things in Judaism called 'rebirth' - see my post on page 1 - so he asks hyperbolically if he's supposed to crawl back into his mother's womb??
Jesus responds by saying not only of water ((physical birth)) but of spirit. Jesus mentions the spirit again and again but never brings up water again to Nicodemus. Jesus isn't talking about baptism. Jesus is talking about the Spirit.
the Jews believed they would inherit the kingdom because they were descended from Abraham through Isaac. they believed their ethnic identity was sufficient, because they are God's chosen people.
Jesus is countermanding that idea. He will only save a remnant, and He will cast out the wicked from among His people: being Jewish does not guarantee salvation.
You say that Jesus isn't talking about Baptism. I strongly disagree. John the Baptist clearly foretells that Jesus will 'Baptize with the Spirit. " Also make no mistake that all Baptism is a ritual performed with water. And when Jesus speaks with Nicodemus there is no reason to assume he is talking about embryotic fluid. All baptism is performed with water.
Mark 1:8 I baptize you
with water, but he will baptize you with
the Holy
Spirit."
Luke 3:16 16John answered them all, "I baptize you with water. But one who is more powerful than I will come,
the straps
of whose sandals I am not worthy to untie. He will baptize you
with the Holy
Spirit and fire.
And, as I said, immediately after Jesus conversation with Nicodemus, Jesus and the Apostles went on a mission of baptizing. John 3:22 Then Jesus and his disciples left Jerusalem and went into the Judean countryside. Jesus spent some time with them there, baptizing people. And they were baptizing with water and the Spirit.
Just before Jesus ascended to heaven, He gave His apostles a new commission, and their mission consisted of baptizing with water and the Spirit:
Matthew 28:16-20 16Then the eleven disciples went to Galilee, to
the mountain where Jesus had told them to go. 17When they saw him, they worshiped him; but some doubted. 18Then Jesus came to them and said, "All authority in heaven and on earth has been given to me. 19Therefore go and make disciples
of all nations,
baptizing them in the name of the Father and of the Son
and of
the Holy
Spirit, 20and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age."
Water has always been an essential part of baptism.
And the baptisms continued after Jesus ascension, with water and the Spirit: Acts 2:38 On the Day of Pentecost, Peter told the crowd, “Repent and be baptized, every one of you, in
the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit” (Acts 2:38). His command concerning baptism was that it be done “in the name
of Jesus Christ.”
Baptism continues to this day, 2,000 years later, a baptism of water and the Spirit. Nothing to do with embryotic fluid.
And, it is foolish to believe that Baptism is just a non essential ritual. Just before Jesus ascended to heaven, He told His apostles, "Whoever believes and is baptized will be saved, but whoever does not believe will be condemned. " Mark 16:16
Does that sound like a non essential ritual to you? And, keep it clear. Jesus was talking about baptism of water and the Spirit.