Jesus continued addressing this subject in John 3:6-8 - "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.' The wind blows where it wishes, and you hear the sound of it, but cannot tell where it comes from and where it goes. So is everyone who is born of the Spirit."
In verse 6, Jesus made a distinction between physical birth and spiritual birth. He did this to help Nicodemus understand that it is the spirit and not the flesh that is "born again." Jesus then stressed the point in verse 7 that none are exempt from this requirement, not even a religious leader like Nicodemus.
Verse 8 is an exceedingly difficult passage of Scripture. It is usually incorrectly cited in an effort to show that as the wind's operations are unknown, so also is the Spirit's mode of operation in the new birth. It should be noted, however, that the text does not compare the wind and the Spirit but the wind and the one born again.
Part of the difficulty of this verse is in the translation of the Greek word pneuma. The word is used several hundred times in the Greek New Testament, and it is rendered "spirit" or "Spirit," but never "wind" (except in the beginning of this verse). If "wind" is changed to "Spirit" here, then the meaning is this: The Spirit breathes or expresses Himself through the word of truth (the gospel), in full harmony with His will and you receive the expression of this will by means of this word; and while you cannot see the Spirit and are thus without visual evidence of His coming and going, it is by means of hearing His voice (as expressed through the word) that you are born again.
If, on the other hand, it is the case that "wind" is actually the correct rendering here, then perhaps Jesus is simply stating that man cannot see the wind, but man can see the effects of the wind; just like one cannot see the spiritual aspect of the new birth, but the effects of the change can be seen (cf. Gal. 5:22,23).
John 3:9-12 reads - "Nicodemus answered and said to Him, 'How can these things be?' Jesus answered and said to him, 'Are you the teacher of Israel, and do not know these things? Most assuredly, I say to you, We speak what We know and testify what We have seen, and you do not receive Our witness. If I have told you earthly things and you do not believe, how will you believe if I tell you heavenly things?"
The Lord's statements were quite perplexing to Nicodemus. Jesus issued a mild rebuke that Nicodemus, as a teacher, should have had some understanding of these matters (cf. Jer. 31:31-34).
In verse 11, when Jesus used the phrase, "You do not receive Our witness," He used the plural pronoun to refer to Nicodemus and all unbelieving Jews. Thus, it is reasonable to understand Jesus' use of "we" and "our" to be referring to those who did know and receive His teaching. Another possibility is that Jesus was referring to Himself and the Holy Spirit as "We."
Jesus continued his mild rebuke in verse 12. Earthly things would include matters relating to this realm like the new birth and the kingdom or church. Heavenly things would include matters beyond the realm of the senses; things that had not yet been revealed, but soon would. Jesus' point is this: If Nicodemus would not believe Jesus when He told him of things he already partially knew, how would he believe when Jesus spoke of that which was utterly unknown to him?
We will continue our study of John 3 tomorrow.