Born again: To experience spiritual birth, God's power must completely renew a person.
Nicodemus thought Jesus was speaking about physical birth. He demonstrated that those in darkness, who do not have spiritual rebirth, cannot understand Jesus or other “heavenly things” (3:12).
Jesus sometimes used ironic misunderstanding as a way to teach. He would say something with a deeper spiritual meaning. The listener would misunderstand his words in a simple or physical way. Then Jesus would explain the deeper meaning.
This method helped people see the difference between earthly thinking and spiritual truth.