The reason of the visit being at night may have been twofold:

1. fear of what others may think
2. to guarantee a long uninterrupted visit

We are not told the amount of time that has passed since the Temple cleansing, but that incident would not have greatly angered the Pharisees since the Temple was the propriety of the Sadducees.  However, the Messianic claims indicated by the cleansing would not have been lost on any good student of the scriptures.

The feud Jesus had started with the Jewish authorities by the Temple incident would certainly have been a deterrent to Nicodemus approaching Him, as would the natural prejudice he would have felt for an untrained Galilean to teach a member of the ruling body of the Jewish nation. Barclay notes that we cannot condemn him for coming at night for it is a wonder that he came to Jesus at all. It was infinitely better for Nicodemus to come at night than to not come. In fact, many of us come to Jesus timidly at first.

“we know” may indicate that Nicodemus was not alone.

This probably took place in the guest chamber of a home in Jerusalem (perhaps that of John?) which would have been on the roof. Nicodemus would have entered by the outside stair. By a later comment of Jesus, it would seem that this was a windy spring night which, when coupled with Jewish superstitions, would have kept most people indoors.

It is quite interesting that the miracles of Jesus had produced a kind of faith in the people that kept Jesus from trusting Himself to them (John 2:23-24). Their faith was what Luther calls a “milk-faith” which required signs for its sustenance. The signs were meant to point to the One in whom faith was to be placed but they missed the point and were touched by the miracles in their minds and not in their hearts. Edersheim notes that these miracles were not recorded because what they spoke of was not recorded on many hearts. However, one heart at least was touched: that of Nicodemus. Faith based on what Jesus does is second place to the faith that is based on Who Jesus is and what He says (John 10:38, 20:29).

John 10:38  But if I do it, even though you do not believe me, believe the miracles, that you may know and understand that the Father is in me, and I in the Father.”

John 20:29  Then Jesus told him, “Because you have seen me, you have believed; blessed are those who have not seen and yet have believed.”

Nicodemus’s concept of Who Jesus was is way too low. He thinks Jesus to be a great teacher and to be a man sent from God, but doesn’t see Him as Messiah, Son of God, and Lord of all. Unfortunately, many who claim to be Christians today have much the same view of Jesus as Nicodemus.