This song is inspired by the words Jesus said, one night, to a certain Pharisee by the name of Nicodimus. Jesus was telling him that we must be born again.
To Nicodimus' amazement, Jesus replied:
"Do not be amazed that I said to you, 'You must be born again.'
The wind blows where it wishes and you hear the sound of it, but do not know where it comes from and where it is going; so is everyone who is born of the Spirit."
(John, 3: 7-8).
Jesus' words mean that as we do not see the wind, but we see the effects of its passing (its sound, its power to cool us and its power to blow things off, etc.), so it is with those born of the Spirit of Jesus. We do not see the Spirit, but we see its effects in the lives of those who receive Him.