Jesus travels to Jerusalem for the annual Passover celebration and while he is there, he receives a visitor during the night. The visitor is a Pharisee named Nicodemus. Nicodemus is also a member of the Jewish Supreme Court, the Sanhedrin. Andreas Kostenberger, in John, Acts: Volume Two (Zondervan Illustrated Bible Backgrounds Commentary), explains that the Sanhedrin is
[h]eadquartered in Jerusalem, [and] it was composed of Pharisees and Sadducees. When Judea became a Roman province in A.D. 6, the Sanhedrin became even more autonomous in handling internal Jewish matters. As John’s Gospel progresses, the Sanhedrin turns out to be the driving force in the plot against Jesus.
Nicodemus introduces himself by acknowledging Jesus as Rabbi (or teacher) and claims that he, and presumably a few other members of the Sanhedrin, recognize that Jesus is sent by God because of the miraculous signs Jesus has been performing in Jerusalem. Although Nicodemus offers restrained respect for Jesus, he clearly does not know who Jesus really is.
Jesus jumps straight to the heart of Nicodemus’s misunderstanding. He does this by telling Nicodemus that anyone who wants to enter heaven (the kingdom of God inaugurated at the end of the age) must be “born again” or “born from above” (either translation is possible). In other words, a person must experience a spiritual rebirth.
Jews at that time had a particular understanding of the future kingdom of God. Kostenberger elaborates:
Jews expected a future kingdom ruled by the Son of David (Isa. 9:1-7; 11:1-5, 10-11; Ezek. 34:23-24; Zech. 9:9-10), the Lord’s Servant (Isa. 42:1 -7; 49:1-7), indeed, the Lord himself (Ezek. 34:11-16; 36:22-32; Zech. 14:9). While not everyone was to be included in this kingdom, Jews in Jesus’ day generally believed that all Israelites would have a share in the world to come, with the exception of those guilty of apostasy or some other blatant sin (m. Sanh. 10:1).
Nicodemus doesn’t understand what Jesus is saying, so Jesus explains again that no human being enters heaven because of biology. Fragile and finite human nature only begets more fragile and finite human nature. The only way for a mortal human to enter heaven is for a spiritual intervention from God Himself. The fact that Nicodemus was born a Jew as a descendant of Abraham and Jacob, and is a devout member of the Pharisees, has no bearing on whether he will enter heaven. The effects of God’s spirit, like the wind, can be seen, but not controlled by human beings.
Nicodemus is shocked at what Jesus is saying, so Jesus asks how it is that a scholar of the Scriptures, a supposed expert on the Hebrew Bible, does not know about the activities of God’s Spirit. Edwin A. Blum, in The Bible Knowledge Commentary, writes,
The Old Testament prophets spoke of the new Age with its working of the Spirit (Isa. 32:15; Ezek. 36:25–27; Joel 2:28–29). The nation’s outstanding teacher ought to understand how God by His sovereign grace can give someone a new heart (1 Sam. 10:6; Jer. 31:33).
Jesus rebukes Nicodemus for not trusting Jesus’s witness about the necessity of spiritual rebirth (earthly things). If Nicodemus does not believe what Jesus tells him about the elementary requirement for entering heaven, then there is no point in Jesus expanding on the grandeur and glory of heaven (heavenly things).
Jesus stresses to Nicodemus that Jesus (the Son of Man) is the only one to ever descend from heaven and then return. He is the only one uniquely qualified to tell Nicodemus about the things of heaven, because that is where Jesus is from. Kostenberger provides further background:
Jesus here contrasts himself, the ‘Son of Man’ (cf. Dan. 7:13), with other human figures who allegedly entered heaven, such as Enoch (Gen. 5:24; cf. Heb. 11:5), Elijah (2 Kings 2:1-12; cf. 2 Chron. 21:12-15), Moses (Ex. 24:9-11; 34:29-30), Isaiah (Isa. 6:1-3), or Ezekiel (Ezek. 1; 10). A whole cottage industry of intertestamental literature revolved around such figures and their heavenly exploits (e.g., 1 En.). While believers can expect to join Christ in heaven one day (cf. John 14:1-3; 17:24), only Jesus came down from heaven as well as ascended back up to heaven (cf. Luke 24:51; Acts 1:9; though note the similar ascent-descent pattern by angels in John 1:51).
Just as Moses lifted up a bronze snake to save the people of Israel from death (Numbers 21:4-9), Jesus will likewise be raised up (a reference to his future crucifixion and resurrection) and so that when people believe in him, they will enter heaven and have eternal life with God.
Verses 16-18 should be read as a unit. John explains, in verse 16, that God the Father loved the sinful world (not just Israel) so much that He sent His one and only Son, Jesus, to the cross, so that everyone who believes in him will go to heaven, and not perish. This verse should remind us of the Old Testament story of Abraham being asked by God to sacrifice his one and only son, Isaac.
Note that John 3:16 delineates both God’s and man’s role in salvation. Gerald Borchert, in vol. 25A, John 1–11, The New American Commentary, explains:
The full perspective is that God is the initiator and principal actor in salvation, and we should never think that salvation originated with us (cf. 1 John 4:9–10). God, however, has given humanity a sense of freedom and requires us to make a choice. Accordingly, people are responsible for their believing. It is unproductive theological speculation, therefore, to minimize either the role of God or of humanity in the salvation process. The Bible and John 3:16 recognize the roles of both.
Verse 17-18 make clear that God’s primary purpose in sending Jesus to the earth was to save people, not condemn them. We must remember that the entire world, because of the sin introduced by Adam and Eve, has been under a type of condemnation since the Fall. It’s not as if the world was morally neutral when Jesus arrived on the scene. This is why John stresses that whoever believes in Jesus is saved, but whoever rejects Jesus has already been condemned.
These verses do not settle the debate about what happens to those who never hear of Jesus, however, because John explicitly connects condemnation in this passage with the rejection of Jesus. But a person who has never heard of Jesus cannot reject Jesus. John is not concerned, in this passage, with those who never hear of Jesus; he is concerned about those who hear and turn away.
Why would anyone reject Jesus? In verses 19-21, John concludes that everyone who loves their sin (darkness) will shun Jesus (the light) because Jesus will expose their sins. They prefer to hide their sins in the dark. D. A. Carson, in The Gospel According to John, The Pillar New Testament Commentary, writes:
As the light of the world (8:12), Jesus is the revelation of God and the objectification of divine holiness and purity. But men loved darkness instead of light: they preferred to live without such knowledge of God, without such brilliant purity. The reason was fundamentally moral: their deeds were evil. They were not willing to live by the truth; they valued their pride more than their integrity, their prejudice more than contrite faith. Worse, anyone in this camp hates the light and refuses to come to it for fear that his deeds will be exposed (elengchthē). The verb suggests not only exposure but shame and conviction (cf. notes on 16:8ff.).