"...unless one is born again he cannot see...[or] enter the kingdom of God....The wind blows where it wishes, and you hear its sound, but you do not know where it comes from or where it goes. So it is with everyone who is born of the Spirit.” John 3:3,5,8
Jesus declared that unless a person is born again – unless he is regenerated, quickened or granted new life by the Spirit of God – he cannot "see" or "enter" the kingdom of God. The word "see" refers not to the perception of physical eyes, but to perception of the heart about spiritual things. That is, unless a person is supernaturally changed by God, he cannot have a heart which understands, or ears to hear or eyes to see the things of God (Deut 29:4; 30:6). Due to his unspiritual nature and corrupted condition it is utterly beyond his human powers to understand the truth about Christ or believe His revelation. The word "enter" refers to participation in kingdom life. That is, unless a man is born from above, he cannot be adopted into God's family. A citizen of God's kingdom must be born into it.
The analogy of birth is used for good reason because as in physical birth, the spiritual birth is not something you do but it something done to you. You are passive and did nothing to make your physical birth happen. Likewise Jesus uses this to communicate the utter reliance we have on the mercy of God if we are to enter His Kingdom. As communicated in John 3:8 it is something that happens by God's sovereign good pleasure, through the power of his Holy Spirit. As you are thus transferred by God from the Kingdom of darkness to the kingdom of light your new spiritual perception, your renewed spiritual nature dictates the desires, tastes and inclinations of your soul. Just as a natural person is inclined to the things of this world, so a child of God has an inclination to the spiritual, that is, the things of the Spirit of God. His new nature inclines him to believe in the truth, beauty and excellency of the gospel of Jesus Christ, and to love, obey, worship and pine after God.
The following is a small collection of helpful biblical resources which discuss John 3:1-8 and the new birth:
MP3s
Regeneration - John 3:1-9 (MP3) by John G Reisinger
Necessity and Nature of the New Birth - John 3 (MP3) by Albert Martin
No New Birth - No Heaven - John 3:1-8 (MP3) Albert Martin
John 3:1-15 - The New Birth (MP3 by Tim Keller
The New Birth - John 3:1-13 (MP3) by Geoff Thomas
The New Birth - John 2:23-3:14 (MP3) by Nicholas T Batzig
The Miracle of the New Birth, Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7 - John 3:1-8 by Steven Lawson
John 3:1-20 (MP3) by Dr Sinclair B Ferguson
Regeneration - John 3 (MP3) by Eric Alexander
The Wind Blows - John 3:1-21 (MP3) by D A Carson
Rebirth - John 3:1-13 (MP3) by R C Sproul
Radical Depravity & Radical Rebirth - John 3:3-8 (MP3) by Joel R Beeke
Born Again - John 3:1-8 (MP3) By Richard Phillips
What Happens in the New Birth? Part 1 - John 3:1-10 (MP3) by John Piper
What Happens in the New Birth? Part 2 - John 3:1-10 (MP3) by John Piper
Born Again - John 3.1-15 by JV Fesko
Text
John 3:3 - Are You Born Again? by J C Ryle
Regeneration - The Christian is Born Again by J I Packer
You Must Be Born Again - John 3:7 by Thomas Boston
What Is the New Birth? by Octavius Winslow
Born Again: A Biblical and Theological Study of Regeneration by Peter Toon
Do You Know the Truth About Being Born Again? by Stephen Pribble
Regeneration: What does it mean to be born again? by Wayne Grudem