What does John 3:3 mean?

Jesus explains that a person cannot be redeemed unless they are "born again." The Greek phrase can also mean "born from above." Nicodemus doesn't fully understand this. People frequently misinterpreted Jesus' spiritual teachings in overly physical ways. The question Nicodemus asks about re-entering a mother's womb (John 3:4) is rhetorical; he knows Jesus cannot mean physical birth. He is asking Jesus to further explain the idea.

This concept of rebirth is critical for understanding the gospel. Children inherit the attributes of their parents: to be a "child of God" is no small thing (John 1:12)! This also implies the associations of change, and pain, involved in childbirth. The change is mostly on the part of the child, but the pain is mostly on the part of the parent. In this case, the pain suffered by God, in the form of Jesus on a cross, produces rebirth and change in those who turn to Him for salvation.