"“Judge not, that you be not judged" (Matthew 7:1) is the most commonly misquoted verse in the entire Bible. As John tells us, "...men loved darkness rather than light, because their deeds were evil. For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed." (John 3:19-20). Thus, when we hear "judge not", it is incredibly tempting to use it as an excuse to say "turn that light off".
But as is often the case, added context changes the interpretation. Rather than being a blanket condemnation of any and all kinds of judgement (except, apparently, the judgement that one is being too judgmental), it is actually a condemnation of hypocrisy. Jesus continues: "For with what judgment you judge, you will be judged; and with the measure you use, it will be measured back to you. And why do you look at the speck in your brother’s eye, but do not consider the plank in your own eye? Or how can you say to your brother, ‘Let me remove the speck from your eye’; and look, a plank is in your own eye? Hypocrite! First remove the plank from your own eye, and then you will see clearly to remove the speck from your brother’s eye. “Do not give what is holy to the dogs; nor cast your pearls before swine, lest they trample them under their feet, and turn and tear you in pieces." (v2-6).
It would be rather odd, if we are not allowed to judge, for Jesus to then tell us not to give what is holy to the dogs, or cast our pearls before swine. How are we to know who is a dog or a swine without first judging them? The clear context here, then, is that we are to avoid hypocritical judgement. We are not to completely ignore sin. In fact, Jesus later tells us "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age.” Amen." (Matthew 28:19-20). Therefore, if scripture says something, we are commanded to preach it, and make disciples who obey it (in other words, we must identify unbelievers, and show them the error of their ways).
The ultimate irony here is that those who misquote Matthew 7:1 are committing the very sin being condemned. When they say "judge not", they are judging you. That is, they have assessed that you are guilty of violating Matthew 7:1, and are attempting to "correct" you. Yet that is exactly what judgement is!
On the flip side, you are not actually breaking the command if you, being clean of a specific sin, offer correction to someone who is guilty of it. The key, of course, is correction. When Christians judge, we cannot condemn, lest we condemn ourselves. No one likes the "holier than thou" type who runs around making your business their business. But another thing no one likes is self-inflicted ruin. Personally, when a brother judges me, I don't see it as hatred, but love. They see me doing something that will harm me, they warn me about it, I hopefully change course, I'm better off for it. That is the true goal of judgement.
But the judgement Christ condemns is the judgement that He alone has the right to deliver. We don't get to run around claiming to be righteous while judging others as scum, because we are only righteous by His merit (and frankly, all too often, so are those whom we hypocritically judge). "Yay! That thief is going to jail!" Ok, have you ever stolen? "Grr! That filthy liar deserves his chops busted!" Have you ever lied? James says it best: "For whoever shall keep the whole law, and yet stumble in one point, he is guilty of all. For He who said, “Do not commit adultery,” also said, “Do not murder.” Now if you do not commit adultery, but you do murder, you have become a transgressor of the law. So speak and so do as those who will be judged by the law of liberty. For judgment is without mercy to the one who has shown no mercy. Mercy triumphs over judgment." (James 2:10-13).
Thus, if the measure we use to judge is meted out to us, we will often condemn ourselves. Those who misapply Matthew 7:1, in particular, may well find that out the hard way. But only a fool despises correction. Christians who judge with the intent to save will likewise be saved. Christians who judge with intent to correct will, themselves, receive correction. Christians who judge in the hope of sparing their brethren destruction will not be destroyed. Christians who judge, desiring to boost their brother's relationship with God, will in turn, come closer to Him.
Thus, Jesus is not telling Christians to turn a blind eye to sin, but rather, not to be blind to their own sin. When we judge, it is to be in the context of iron sharpening iron (Proverbs 27:17). Those who hate such judgments will often end up forfeiting the privilege. They grow dull, rusty, and ultimately useless to the Kingdom. Hindering it, even, though by God's grace, He will compensate for our failures. This, however, is not license to fail. We must, as Christ commanded, "...judge with righteous judgment.”" (John 7:24).
Let us therefore echo the words of Christ: "I can of Myself do nothing. As I hear, I judge; and My judgment is righteous, because I do not seek My own will but the will of the Father who sent Me." As we hear, in scripture, we should do well to observe, but also, in step with the Great Commission, teach people to do likewise, seeking the will of God, who has sent us out for that very purpose. Let us call sinners to repentance, "And have no fellowship with the unfruitful works of darkness, but rather expose them." (Ephesians 5:11). In Jesus' name, amen.