John 3:17-21 — For God sent not His Son into the world to condemn the world; but that the world through Him might be saved.
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.
And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.
condemn = judge — And if any man hear My words, and believe not, I judge him not: for I came not to judge the world, but to save the world (John 12:47). He'll come as a judge at His second coming.
Verse 17 enlarges the purpose of God's love
might = expresses design. — "should be saved"
Christ didn't come to judge, but the world is already condemned because of unbelief.
Verily, verily, I say unto you, He that heareth My word, and believeth on Him that sent Me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life (John 5:24).
Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God (Romans 3:19).
There are two (and only two) kinds of people (verse 18).
not condemned — (see my post on Romans 8:1)
light shows the heart of man (see my post on John 1:6-8)
But all things that are reproved are made manifest by the light: for whatsoever doth make manifest is light. Wherefore he saith, Awake thou that sleepest, and arise from the dead, and Christ shall give thee light (Ephesians 5:13-14).
When people refuse Christ, their deeds will always prove evil — evil motives
People do not come to Christ by choice.
Verse 19 — "This is how the judgment works." The sentence is pronounced because of this.
Verse 19 gives the cause of humanity's unbelief — People are in the dark and they love it. They prefer ignorance because they are evil.
hateth the light — People don't want to be known for what they really are. Nor do they want to part from the evil they love.
lest his deeds — People refuse to read the Bible because they know it would condemn them.
cometh (verse 21) = "comes again and again"
doeth truth — come to Christ, the light
When people trust Christ, their deeds are the fruit of the Spirit.
For ye were sometimes darkness, but now are ye light in the Lord: walk as children of light: For the fruit of the Spirit is in all goodness and righteousness and truth (Ephesians 5:8-9).