John 3:9-14 Nicodemus answered and said unto him, How can these things be? Jesus answered and said unto him, Art thou a master of Israel, and know not these things? Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness. If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things? And no man hath ascended up to heaven, but he that came down from heaven, even the Son of man which is in heaven. And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up
The question Nicodemus asked Christ should have been clear to him if he had known such Scripture as Jeremiah 31:33; 32:39; Ezekiel 11:19; 18:31; 36:25-27; Psalm 51:10; Isaiah 1:18-20; 55:6 which says “I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.”
‘Art thou a master of Israel, and know not these things?’ Jesus expected him to know the Scriptures enough to be saved, but he was like most people today, even many ministers who do not know what the new birth is.
‘You receive not our witness’ This is the only hint that Nicodemus at this time went away in doubt about spiritual things, but later it is clear he accepted them (John 19:39).
The earthly things in this passage are in John 3:6 and 8 and the heavenly in John 3:3, 5, 6 and 8.
The Greek word for ‘ascended up’ is anabaino which means to go up of own power, not taken up as was Enoch (Gen. 5:24; Heb. 11:5), Elijah (2Kin. 2:11), Paul (2Cor. 12:1-3), and John (Rev. 4:1). This refers to the ascension of Christ (John 3:13; 6:62; Acts 1:11; Lk. 24:51; Eph. 4:8-10). Christ ascended and came back before His final ascension to heaven to stay (John 20:17).
The verse ‘is in heaven’ proves that Jesus had already ascended when John wrote this book; that the conversation with Nicodemus ended with John 3:12; and that Jesus was now in heaven.
The fourth New Testament prophecy in John that is fulfilled ‘And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up (Num. 21:9; John 8:28; 12:32, 34; 1Pet. 2:24). It behoved Christ to be crucified in order to fulfil prophecy and to redeem man (Lk. 24:26, 46; Acts 3:18; 17:3).