John 3  Nicodemus comes to see Jesus and admits that they, the Jewish leaders, know that He, Jesus, came from God, because they know that the signs that He does cannot be done unless God is involved.  If Nicodemus knew that, then the rest should have known it too!  They just refused to admit it...

Jesus and Nicodemus have an interesting conversation that we have read over and over again.
Jesus speaks of being born again.  Nicodemus thinks of physical birth.
Jesus speaks of spiritual birth.  Nicodemus doesn't understand.
Verse 11 " Truly, truly, I say to you, we speak that which we know, and bear witness of that which we have seen, and you do not receive our witness."   This is Jesus speaking, but He uses the pronoun - we,( perhaps including the Holy Spirit?)  John the Baptist states in verse 31-32, " He who comes from above is above all... What He has seen and heard, of that He bears witness; and no man receives His witness." 

John, the disciple, wrote in 1st John 1:1-3 " What was from the beginning, what we have heard, what we have seen with our eyes, what we beheld and our hands handled, concerning the Word of Life and the life manifested, and we have seen and bear witness and proclaim to you the eternal life, which was with the Father and was manifested to us - what we have seen and heard we proclaim to you also, that you also may have fellowship with us and indeed our fellowship is with the Father and with His Son Jesus Christ."  

To bear witness - to give testimony to or report or give evidence;  This is what Jesus did.  He came to tell the world the Truth - what He knew, what He saw,  what He heard;  this He testified of when He spoke.   And, the religious leaders refused to believe that which He spoke.

It is like a jury during a trial.  They hear the testimony of a witness, one who saw first hand the event and who tells what he saw and heard.  But the jury doesn't believe that the witness is telling the truth. They ignore his testimony and make decisions based on their own perceptions.

Jesus tells us that no one else has ascended into heaven and descended to the earth except Him.  Only He is able to testify to what is seen and heard there.  John the baptist's testimony seconds this. " He who comes from above is above all.... "   Jesus tells Nicodemus that:
1. The Son of man will be lifted up.
2. Believing in Him is what results in eternal life.
3. God loves the world and gave His Son for the world.
4. He came for salvation not for judgement.
5. Judgement has already happened to the unbeliever, because they are all guilty of evil deeds.
6. Those who believe will walk in the Truth and practice the truth because they have come out of the dark and into the light.

 In other words,  we have all sinned and come short of the glory of God.  Jesus knows what the glory of God is.. He saw it and heard it and came to tell us about it.  He gave His own life that we might know the glory of the Lord ourselves.  And the only way we can do that is through believing Him.  Believing His testimony and following Him.

" He who believes in the Son has eternal life; but he who does not obey the Son shall not see life, but the wrath of God abides in him. " verse 36

Father, we trust and obey Your Son, the living Word of Life.  Lead us always to the Truth through our Lord and Savior who came from You to testify of Your Love and forgiveness.  O, help us to walk in Your Light all the day long. Amen