'Necessary' in the Bible

Do not be surprised that I say to you, It is necessary for you to have a second birth.

As the snake was lifted up by Moses in the waste land, even so it is necessary for the Son of man to be lifted up:

And it was necessary for him to go through Samaria.

Then the people in answer said to him, The law says that the Christ will have life without end: how say you then that it is necessary for the Son of man to be lifted up? Who is this Son of man?