You see the leaves that are caught up in the wind. You see the little swirls of dust. You feel the wind on your face. The problem was that Nicodemus, like all human beings, was of the flesh. He was from the earth.
Flesh is mortal.
It is subject to death, decay, and corruption. Many people try everything imaginable to ignore or forget this, but the fact always remains. The truth is that we dwell in a mortal body which will soon return to dust. The Answer Our old state, our old nature, and even all our good deeds are insufficient. God is totally and absolutely holy and righteous.