We are commanded by Jesus to judge righteous judgment (John 7:24).
Righteous judgment is basically judging from a biblical or godly perspective.
We are not to judge unrighteously or hypocritically.
Judging unrighteously would be calling what God calls evil as good and calling what God calls good as evil (Proverbs 17:15, Isaiah 5:20-23, ).
Hypocritical judgment would be judging others for things we are guilty of ourselves or doing something similar (Matthew 7:1-5).
The often quoted “Matthew 7:1- Judge not that ye be not judged” whenever anyone speaks against any particular sin or wrongdoing or someone doing something sinful is speaking of hypocritical judgment.
It is not a universal condemnation of judgment but a condemnation of hypocritical judgment.
We are told before we can judge righteously, properly or biblically we must remove the sin from our own life to see clearly to help them remove theirs (Matthew 7:5).
This is not spoken of as some impossibility or something we should not expect to attain unto.
Much of the remainder of Matthew 7 is dealing with the subject of proper biblical, righteous judgment.
We are told to judge between the holy and the dogs (Matthew 7:6).
We are told to judge between what are pearls and what are swine (Matthew 7:6).
In Matthew 7:13-14 we are told to judge between a broad road that leads to destruction that most are on and a straight and narrow way that leads to life.
After this we are told exactly who is on which road and how to judge who is on which road.
In Matthew 7:15 Jesus told us to “beware of false prophets”.
To know if someone is true or false, right or wrong, real or fake requires us to make a judgment.
We must judge their words.
We must judge their actions.
We must judge their fruits.
In Matthew 7:16-23 we are told to judge a tree by its fruit.
The only way to know what kind of a tree (person) we are dealing with is to judge their fruits (actions, words, lifestyle).
If the actions, words, fruits, deeds line up with the scripture we can give the benefit of the doubt we are dealing with a good tree (Matthew 7:16-20, Matthew 12:33-37).
If the actions, words, fruits deeds are sinful then we are dealing with a bad tree and the person is unsaved.
In 1 John 3:6-10 we are told how to know the difference between a child of God (believer, follower of Christ, Christian, righteous) and a child of the devil (sinner, unrighteous).
In Malachi 3:18 we are told to be able to discern (judge) between him that serves God and him that serves Him not.
1 Corinthians 2:14-16 states the spiritual man judges all things and uses the terms judge and discern interchangeably.
The Bible states the saints shall judge in things that pertain to this life (1 Corinthians 6:2-3).
The Bible many times has lists of people who live in, practice, commit sins who will not go to heaven and will end up in hell (1 Corinthians 6:9-10, Galatians 5:19-21, Ephesians 5:5, Revelation 21:8).
If it is certain and obvious a certain person is committing these acts or sins then it is a biblical certainty they are not saved, not a Christian, and are presently heading to hell.
This is a making a righteous judgment based upon biblical fruit.
Christians are not to judge one another on matters that are not salvational (Romans 14).
All judgments of actions or people should be based upon genuine biblically motivated love, for the love of God, the glory of God, and for the love and concern of the souls of people.
It is possible for people to make a proper biblical judgment with a wrong spirit not motivated by genuine biblical love.
However at this point in our culture what has been more of a point of contention is if any person anywhere speaks against sin, rebukes sin sharply, or claims a person is not saved and must repent and they are headed to hell is that they are not to judge and therefore have a wrong motive and a wrong spirit.
This is not true.
Biblical preaching involves rebuking and reproving sin (2 Timothy 4:2, Titus 1:13).
Rebuke is a sharp, personal, public correction of sin.
Reprove means to expose sin and is the same word as convict (John 16:8, Ephesians 5:11, 2 Timothy 4:2).
It is our job and responsibility to do the rebuking and reproving as long as we are motivated by biblical love for God, for truth, for souls, etc.
Just because it is not received or appreciated it does not mean the motive or spirit was wrong or bad.
Jesus showed His love by those in sin by rebuking them in their sin and urging them to repent (Revelation 3:19).
Jesus came for the purpose of calling sinners to repent (Luke 5:32, Matthew 9:13, Mark 2:17) and He commands us to do the same (Luke 24:47, Acts 17:30-31, Acts 20:21, Acts 26:20).
It is biblically impossible and unncessary to preach repentance to sinners without judging, naming, their sins and the consequences of their sins.
You must name and judge sin when preaching repentance to sinners.
If you do not deal with the subject of repentance when dealing with sinners then you are not dealing biblically with sinners (Matthew 3:1-2, Matthew 4:17, Mark 1:1-4, Mark 1:14-15, Mark 6:12, Luke 5:32, Luke 13:3,5, Luke 24:47, Acts 2:38, Acts 3:19, Acts 17:30-31, Acts 20:21, Acts 26:20).
When the Bible speaks of God judging them that are outside of the church it is speaking of church discipline and is not an excuse not to deal with and speak against sin because you are not supposed to judge them (1 Corinthians 5:12-13).
Jesus told Simon “Thou hast rightly judged” (Luke 7:43).
Jesus said “Yea and why even of yourselves judge ye not what is right” (Luke 12:57).
Psalm 37:30 says the tongue of the righteous talketh of judgement.
People everyday everywhere are always judging certain things as right or wrong as well as certain people.
Most people would definitely admit and judge being a pedophile, rapist, murderer, etc is wrong and they are wrong.
We obviously of course do not execute judgment as far as casting people into hell or allowing them into heaven.
That is God’s responsibility.
It is our responsibility to pronounce or proclaim judgment upon the sins God has already pronounced judgment upon.
This is very basic and much more could be said but this should answer many questions for those who believe or have been taught it is unbiblical to judge.