Thank you my dear friend for a great question! Well, Nicodemus must have either personally listened to or heard of the teachings of the Lord Jesus and must have either seen or heard of His mighty works, most of which were prophesies regarding the Messiah (see Isaiah 35 and Isaiah 61). I believe that as a result of what he had witnessed or heard about Jesus, Nicodemus rightly sensed in his heart that the Lord Jesus had been sent from God, and that His teachings were truth. I do not know that he realized as yet that Jesus was in fact “Emmanuel”, meaning “God with us”; but I’m sure this was part of his reason for going to Jesus…to find out who He truly was.   Sensing the faith of Nicodemus, and the true need of his soul, the Lord Jesus began to teach him, but Nicodemus had trouble understanding what the Lord Jesus was saying-without the Holy Spirit, Nicodemus could only look at the truths being presented to him through the eyes of the flesh-his old nature, and this same is true for each of us.

Thus, while Nicodemus certainly knew some things about the Kingdom of God, he clearly did not understand about the need for the new birth in order to comprehend or enter the Kingdom. Thus, you ask rightly, “what should he have known as a teacher of the people?” Well, Nicodemus clearly knew the Old Testament Scriptures, which would have pointed to not only the words and works of the Christ, which I believe Nicodemus had recognized; but also, Nicodemus certainly knew something about the coming of the Kingdom of God, and the Holy Spirit being placed into the hearts of the believing remnant of Israel. I’m sure Nicodemus was aware of Ezekiel 36:24-28, though it appears that he did not understand the full application as it applies to being born again: “For I will take you from among the heathen, and gather you out of all countries, and will bring you into your own land…A new heart also will I give you, and a new spirit will I put within you…And I will put My spirit within you, and cause you to walk in My statutes…And ye shall dwell in the land that I gave to your fathers; and ye shall be My people, and I will be your God.”

Now, while Nicodemus knew many things in Scripture, and he truly sensed his need to come to Jesus for His teaching, he was as yet without the Spirit of God who was needed in order that he might understand heavenly truths (See 1 Corinthians 2:14). In John 14:26, we see the role of the Holy Spirit in the hearts of God’s children.  The Lord Jesus said, “But the Comforter, which is the Holy Ghost, whom the Father will send in My name, He shall teach you all things…” Again, Nicodemus, before spiritual rebirth, could only comprehend in terms of the flesh. He understood only in a literal manner according to his knowledge of natural things and wondered at how a person might be born of his mother the second time.  But Jesus explained in John 3:5-6 that there was a need for him to be born of water and the Spirit.  This of course does not refer to physical birth, nor does it refer to water baptism as the means of obtaining the Holy Spirit. In the Scriptures, “water” can refer to the Word of God or to the Holy Spirit. I understand too that the phrase could rightly be translated “of water, even the Spirit”. In any case, in order for Nicodemus to understand the heavenly truths regarding entrance into the Kingdom of God, he needed a fundamental change in his nature; not just teaching to improve the flesh, but new life (life from above) through the power of the Holy Spirit.  And so it is for us all! “That which is born of the Spirit is spirit”.  Thankfully, by the Grace of our Lord Jesus, Nicodemus did, I believe, come ultimately to be born again (see John 7:50 and John 19:39). It is my heart’s prayer that all who read this response are likewise “born again”! May the Lord bless His Word to your heart.  (SF)  (493.5)