Take a look at Numbers 21:4-9, That's what Jesus told Nicodemus to do when he considered who Jesus actually was. Nicodemus thought that Jesus had the makings of a prodigy teacher, which is why he probably went to see him under the security of the night, but Nicodemus left that conversation with more questions than answers. I imagine he left the meeting with Jesus thinking, "That didn't go how I thought it was going to go..." Nicodemus likely thought that in this meeting he would flex his intellect and press Jesus into submission, but it went exactly the other way. Jesus gave Nicodemus the gospel and clearly explained who He was and why He was here, yet Nicodemus still missed it. Nicodemus was the "Teacher of Israel" and yet he failed to understand that Jesus was salvation for the people.