Just about any time there is a discussion about a moral question, in which any reference is made to what the Scriptures or the teachings of the Church say on the issue, you will inevitably hear this passage is cited. And when it is cited, it is almost always used to shut down any discussion of what is right and wrong, and the assumption seems to be that everyone get's to decide for themselves what they believe to be moral, and no one else has any right to challenge the conclusions of anyone else. You even hear this passage used in this way by Christians, and even Orthodox Christians. But is this a correct understanding of what Christ said?
Let's consider the immediate context of the passage:
“Judge not, that ye be not judged. For with what judgment ye judge, ye shall be judged: and with what measure ye use, it shall be measured back to you. And why beholdest thou the speck that is in thy brother's eye, but considerest not the beam that is in thine own eye? Or how wilt thou say to thy brother, Let me pull out the speck out of thine eye; and, behold, a beam is in thine own eye? Thou hypocrite, first remove the beam out of thine own eye; and then shalt thou see clearly to remove the speck out of thy brother's eye" (Matthew 7:1-5).
St. John Chrysostom goes into a great deal of detail on the meaning of this. He begins his homily on this passage by rhetorically asking: "What then? Ought we not to blame them that sin? Because Paul also saith this selfsame thing: or rather, there too it is Christ, speaking by Paul, and saying, “Why dost thou judge thy brother? And thou, why dost thou set at nought thy brother?” (Romans 14:10) and, “Who art thou that judgest another man’s servant?” (Romans 14:4). And again, “Therefore judge nothing before the time, until the Lord come” (1 Corinthians 4:5). How then doth He say elsewhere, “Reprove, rebuke, exhort,” (2 Timothy 4:2) and, “Them that sin rebuke before all?”(1 Timothy 5:20). And Christ too to Peter, “Go and tell him his fault between thee and him alone,” and if he neglect to hear, add to thyself another also; and if not even so doth he yield, declare it to the church likewise?” (Matthew 18:15-17). And how hath He set over us so many to reprove; and not only to reprove, but also to punish? For him that hearkens to none of these, He hath commanded to be “as a heathen man and a publican” (Matthew 18:17). And how gave He them the keys also? since if they are not to judge, they will be without authority in any matter, and in vain have they received the power to bind and to loose (Matthew 16:19; John 20:23). Homily 23 on the Gospel of St Matthew
St. John then points out that no household could function, and no society could maintain order if this were taken to mean that we should exercise no judgment of any kind, and then he says:
"But if to many of the less attentive, it seem yet rather obscure [i.e., the meaning of this passage], I will endeavor to explain it from the beginning. In this place, then, as it seems at least to me, He doth not simply command us not to judge any of men’s sins, neither doth He simply forbid the doing of such a thing, but to them that are full of innumerable ills, and are trampling upon other men for trifles. And I think that certain Jews too are here hinted at, for that while they were bitter accusing their neighbors for small faults, and such as came to nothing, they were themselves insensibly committing deadly sins. Herewith towards the end also He was upbraiding them, when He said, “Ye bind heavy burdens, and grievous to be borne, but ye will not move them with your finger” (Matthew 23:4) and, “ye pay tithe of mint and anise, and have omitted the weightier matters of the law, judgment, mercy, and faith” (Matthew 23:23). Well then, I think that these are comprehended in His invective; that He is checking them beforehand as to those things, wherein they were hereafter to accuse His disciples. For although His disciples had been guilty of no such sin, yet in them were supposed to be offenses; as, for instance, not keeping the sabbath, eating with unwashen hands, sitting at meat with publicans; of which He saith also in another place, “Ye which strain at the gnat, and swallow the camel” ((Matthew 23:24). But yet it is also a general law that He is laying down on these matters. And the Corinthians too Paul did not absolutely command not to judge, but not to judge their own superiors, and upon grounds that are not acknowledged; not absolutely to refrain from correcting them that sin. Neither indeed was He then rebuking all without distinction, but disciples doing so to their teachers were the object of His reproof; and they who, being guilty of innumerable sins, bring an evil report upon the guiltless. This then is the sort of thing which Christ also in this place intimated; not intimated merely, but guarded it too with a great terror, and the punishment from which no prayers can deliver."
So according to St. John Chrysostom, what Christ and St. Paul were warning against in the passages that speak of not judging is that we should not judge others over small things when we are guilty of much worse, and we should not judge when we do not have sufficient information to do so, especially when it comes to those who are in authority. However, we certainly can rebuke and reprove those who are guilty of sins, when the facts warrant it. But in our day, even saying that something is a sin is considered to be a violation of this teaching of Christ. But St. John clearly rejects that idea:
“What then!” say you: “if one commit fornication, may I not say that fornication is a bad thing, nor at all correct him that is playing the wanton [the sexually immoral]?” Nay, correct him, but not as a foe, nor as an adversary exacting a penalty, but as a physician providing medicines. For neither did Christ say, “stay not him that is sinning,” but “judge not;” that is, be not bitter in pronouncing sentence.”
St. John defends correcting the sinner, but cautions that we should do so gently and lovingly. He does not even directly address the question of whether or not one can say that fornication is a bad thing, because he clearly considers the answer to that question to be obvious... and obviously "yes".
He then goes on to cite more examples of what Christ actually is talking about in this passage:
"Yea, for many now do this; if they see but a monk wearing an unnecessary garment, they produce against him the law of our Lord,while they themselves are extorting without end, and defrauding men every day. If they see him but partaking rather largely of food, they become bitter accusers, while they themselves are daily drinking to excess and surfeiting: not knowing, that besides their own sins, they do hereby gather up for themselves a greater flame, and deprive themselves of every plea. For on this point, that thine own doings must be strictly inquired into, thou thyself hast first made the law, by thus sentencing those of thy neighbor. Account it not then to be a grievous thing, if thou art also thyself to undergo the same kind of trial."
So the point is that indeed, the measure you apply to others will be measured back to you, and so if you are not prepared to have the same standard applied to yourself, you should not put yourself into the position of judging others over things that you yourself are guilty, and perhaps even moreso.
And although, as St. John Chrysostom points out, that St. Paul also warns against judging, in 1st Corinthians St. Paul chides the Corinthians for being too tolerance of sin in their midst, and for not judging:
"It is actually reported that there is sexual immorality among you, and such sexual immorality as is not even named among the Gentiles—that a man has his father’s wife! And you are puffed up, and have not rather mourned, that he who has done this deed might be taken away from among you. For I indeed, as absent in body but present in spirit, have already judged (as though I were present) him who has so done this deed. In the name of our Lord Jesus Christ, when you are gathered together, along with my spirit, with the power of our Lord Jesus Christ, deliver such a one to Satan for the destruction of the flesh, that his spirit may be saved in the day of the Lord Jesus.... I wrote to you in my epistle not to keep company with sexually immoral people. Yet I certainly did not mean with the sexually immoral people of this world, or with the covetous, or extortioners, or idolaters, since then you would need to go out of the world. But now I have written to you not to keep company with anyone named a brother, who is sexually immoral, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner—not even to eat with such a person. For what have I to do with judging those also who are outside [the Church]? Do you not judge those who are inside? But those who are outside [the Church] God judges. Therefore “put away from yourselves the evil person. Dare any of you, having a matter against another, go to law before the unrighteous, and not before the saints? Do you not know that the saints will judge the world? And if the world will be judged by you, are you unworthy to judge the smallest matters? Do you not know that we shall judge angels? How much more, things that pertain to this life? If then you have judgments concerning things pertaining to this life, do you appoint those who are least esteemed by the church to judge? I say this to your shame. Is it so, that there is not a wise man among you, not even one, who will be able to judge between his brethren? But brother goes to law against brother, and that before unbelievers! No, you yourselves do wrong and cheat, and you do these things to your brethren! Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived. Neither fornicators, nor idolaters, nor adulterers, nor the effeminate, nor homosexuals, nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners will inherit the kingdom of God. And such were some of you. But you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus and by the Spirit of our God. (1st Corinthians 5:1-5;5:9-6:10).
We should judge with fear and trembling, because we will be judged by the same standard. We should not judge those matters about which we do not have sufficient information to judge. We should be hesitant to judge those who are in authority over us, and likewise we should be hesitant to judge those who are not under our authority. We should never presume to know anyone’s ultimate fate at the judgment, which belongs only to God. We should also be loving and gentle when rebuking a brother or sister about their personal sin. But we have to be clear on what sin is. And we have to obey the words of Christ and St. Paul when it comes to maintaining discipline in the Church. We often have to judge, but we must "judge with righteous judgment” (John 7:24).