Searcher:
Some insight can be obtained by comparing two accounts that are seperated by about three years of time. I'll paste them here first for easy reference:
(John 3:1-17) 3 ... Nic·o·de′mus ... 2 ... came to him [Jesus] in the night ... 3 ... Jesus said to him: "Most truly I say to you, Unless anyone is born again, he cannot see the kingdom of God." 4 Nic·o·de′mus said to him: "How ... ? ... 5 Jesus answered: "Most truly I say to you, Unless anyone is born from water and spirit, he cannot enter into the kingdom of God. 6 What has been born from the flesh is flesh, and what has been born from the spirit is spirit. 7 Do not marvel because I told you, YOU people must be born again. 8 ... 9 In answer Nic·o·de′mus said to him: "How can these things come about?" 10 In answer Jesus said to him: "Are you a teacher of Israel and yet do not know these things? 11 Most truly I say to you, What we know we speak and what we have seen we bear witness of, but YOU people do not receive the witness we give. 12 ... 13 ... 14 And just as Moses lifted up the serpent in the wilderness, so the Son of man must be lifted up, 15 that everyone believing in him may have everlasting life. 16 "For God loved the world so much that he gave his only-begotten Son, in order that everyone exercising faith in him might not be destroyed but have everlasting life. 17 For God sent forth his Son into the world, not for him to judge the world, but for the world to be saved through him.
(Much was edited out of Jn 3:1-17 to get to the main points)
(Matthew 19:16-29) 16 Now, look! a certain one came up to him and said: "Teacher, what good must I do in order to get everlasting life?" 17 He said to him: ... 18 ... Jesus said: "Why, You must not murder, ... 20 The young man said to him: "I have kept all these ... what yet am I lacking?" 21 Jesus said to him: "If you want to be perfect, go sell your belongings ... and you will have treasure in heaven ... 22 ... the young man ... went away grieved ... 23 But Jesus said to his disciples: "Truly I say to YOU that it will be a difficult thing for a rich man to get into the kingdom of the heavens. 24 Again I say to YOU, It is easier for a camel to get through a needle's eye than for a rich man to get into the kingdom of God." 25 When the disciples heard that, they expressed very great surprise, saying: "Who really can be saved?" 26 Looking them in the face, Jesus said to them: "With men this is impossible, but with God all things are possible." 27 Then Peter said to him in reply: "Look! We have left all things and followed you; what actually will there be for us?" 28 Jesus said to them: "Truly I say to YOU, In the re-creation, when the Son of man sits down upon his glorious throne, YOU who have followed me will also yourselves sit upon twelve thrones, judging the twelve tribes of Israel. 29 And everyone that has left houses or brothers or sisters or father or mother or children or lands for the sake of my name will receive many times more and will inherit everlasting life.
(Much edited to get to the main points)
Now for some comparisons:
The section in John occurs near Passover of 30. The section from Matthew occurs near Passover of 33. Three years apart. (I'm using the Society's dating here.) Timewise, the main difference is the three years.
Now notice in John: Being "born again," 'seeing the Kingdom of God,' being "born from water and spirit," being "born from the spirit," "believing in him [Jesus]," 'having everlasting life,' 'that everyone exercising faith in him might have everlasting life,' and "for the world to be saved through him." are all part of the same discussion. (Some commentators says that Jesus' words end at verse 15 and John adds his comments starting in verse 16. Most, though, say Jesus' words extend to about verse 21.)
Moreover, Jesus chides Nicodemus for not knowing these things despite his being a "teacher in Israel." The implication of this is that these things were taught in the OT. Most probably Jesus has Jer 31:31-33 and possibly other similar verses in mind. Thus, Jesus could not have been referring to going to heaven - that was a surprise, even for the disciples.
Notice also, in the discussion with Nicodemus, Jesus says in verse 11: " ... What we know we speak and what we have seen we bear witness of, but YOU people do not receive the witness we give." In other words, what Jesus said is not just what "HE" was saying, but was what "WE" [Jesus and his disciples, based on the context also which stretches back to 2:13] were preaching about. Thus, what Jesus was describing to Nicodemus was also understood by his disciples.
Now, three years later in the discussion with the rich ruler: 'Getting everlasting life,' 'having treasure in heaven,' 'getting into the kingdom of the heavens,' and 'getting into the kingdom of God' are all tied together by Jesus as being the same thing. Then the disciples asked, "Who really can be saved?" They understood Jesus' references to life and the Kingdom to 'being saved.'
They then ask Jesus, 'what will there be for us?' [his then present disciples]. Jesus goes on to explain about sitting on thrones and judging.
The conclusion: What Jesus was talking about to Nicodemus, with reference to being 'born from water and spirit' was not referring to sitting on thrones and judging, nor to going to heaven. It was what all possible disciples of Jesus would have to experience.
In Romans 6:1-7, baptism is equated with dying and coming to life again.
I hope an analysis of these thoughts will help.
Take Care