Nicodemus comes to Jesus by night
Nicodemus, a Pharisee and member of the ruling council, came to Jesus at night. Jesus told him that no one can see God's Kingdom without being born anew, of water and the Spirit.
For God so loved the world, that he gave his only born Son, that whoever believes in him should not perish, but have eternal life.
John 3:16 (World English Bible)
Jesus compared himself to the bronze serpent Moses lifted up in the wilderness (Numbers 21:8–9): the Son of Man too must be lifted up, so that everyone who believes may have eternal life. Nicodemus reappears later, defending Jesus before the council (John 7:50–51) and helping to bury him (John 19:39).
Dating notes
During the Passover visit of AD 30 (John 2:23; 3:1). The month shown is estimated from the order of events in Ussher's harmony, so that events of the same year appear in sequence.