John 3

The teachings of the Savior to -

"...a man of the Pharisees, named Nicodemus, a ruler of the Jews..." (New Testament | John 3:1)

Provides the gospel reader with some of the most profound and complete doctrine of the plan of salvation. Among other things, he recalls the works of Moses, the very prophet from which the very Mosaic law they professed to believe, saying

"...as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:
15 That whosoever believeth in him should not perish, but have eternal life." (New Testament | John 3:14 - 15)

And then the Savior taught the very core of the gospel plan -

"For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved." (New Testament | John 3:16 - 17)

In other words as Amulek taught -

"...that the Lord surely should come to redeem his people, but that he should not come to redeem them in their sins, but to redeem them from their sins." (Book of Mormon | Helaman 5:10)

There have been some political opinions discussed recently whether there is a heaven or hell. In these teachings of the Savior, I believe He is teaching Nicodemus the qualifications to receive of His fulness or in other words, enter the Celestial Kingdom explaining -

"He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God." (New Testament | John 3:18)

"condemned already" suggests that He will not save them in their sins. And then the Savior explains the doctrine of condemnation, or damnation teaching -

"...this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God." (New Testament | John 3:19 - 21)

"Should not perish, but have everlasting life" is one the "doeth" truth and cometh to the light.