The Testimony of Jesus

"How can these things be?" asked Nicodemus.
"Are you a teacher of Israel and don’t know these things?" Jesus replied. "I assure you: We speak what We know and We testify to what We have seen, but you do not accept Our testimony. If I have told you about things that happen on earth and you don't believe, how will you believe if I tell you about things of heaven? No one has ascended into heaven except the One who descended from heaven—the Son of Man. Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up, so that everyone who believes in Him will have eternal life. (John 3:9-15 HCSB)

The One who comes from above is above all. The one who is from the earth is earthly and speaks in earthly terms. The One who comes from heaven is above all. He testifies to what He has seen and heard, yet no one accepts His testimony. The one who has accepted His testimony has affirmed that God is true. For God sent Him, and He speaks God’s words, since He gives the Spirit without measure. The Father loves the Son and has given all things into His hands. The one who believes in the Son has eternal life, but the one who refuses to believe in the Son will not see life; instead, the wrath of God remains on him. (John 3:31-36 HCSB)

Nobody has been to heaven. But the one from heaven had come down to earth, yet we do not believe Him. We rather believe in those who were from earth, who speak of things of heaven as if they had been there.