Judge not ... - This command refers to rash, censorious, and unjust judgment. See Romans 2:1. Luke Luke 6:37 explains it in the sense of “condemning.” Christ does not condemn judging as a magistrate, for that, when according to justice, is lawful and necessary. Nor does he condemn our “forming an opinion” of the conduct of others, for it is impossible “not” to form an opinion of conduct that we know to be evil. But what he refers to is a habit of forming a judgment hastily, harshly, and without an allowance for every palliating circumstance, and a habit of “expressing” such an opinion harshly and unnecessarily when formed. It rather refers to private judgment than “judicial,” and perhaps primarily to the customs of the scribes and Pharisees.

With what judgment ... - This was a proverb among the Jews. It expressed a truth; and Christ did not hesitate to adopt it as conveying his own sentiments. It refers no less to the way in which people will judge of us, than to the rule by which God will judge us. See 2 Samuel 22:27; Mark 4:24; James 2:13.
Mete - Measure. You shall be judged by the same rule which you apply to others.

And why beholdest thou the mote ... - A mote signifies any “light substance,” as dry chaff, or fine spires of grass or grain. It probably most usually signified the small “spiculae” or “beards” on a head of barley or wheat. It is thus placed in opposition to the word “beam.”
Beam - The word used here signifies a large piece of squared timber. The one is an exceedingly small object, the other a large one. The meaning is, that “we are much more quick and acute to judge of small offences in others, than of much larger offences in ourselves.” Even a very “small” object in the eye of another we discern much more quickly than a much larger one in our own; a small fault in our neighbor we see much more readily than a large one in ourselves. This was also a proverb in frequent use among the Jews, and the same sentiment was common among the Greeks, and deserves to be expressed in every language.

Thou hypocrite, first cast out ... - Christ directs us to the proper way of forming an opinion of ethers, and of reproving and correcting them. By first amending our own faults, or casting the beam out of our eye, we can “consistently” advance to correct the faults of others. There will then be no hypocrisy in our conduct. We shall also “see clearly” to do it. The beam, the thing that obscured our sight, will be removed, and we shall more clearly discern the “small” object that obscures the sight of our brother. The sentiment is, that the readiest way to judge of the imperfections of others is to be free from greater ones ourselves. This qualifies us for judging, makes us candid and consistent, and enables us to see things as they are, and to make proper allowances for frailty and imperfection.

Give not that which is holy ... - By some the word “holy” has been supposed to mean “flesh offered in sacrifice,” made holy, or separated to a sacred use; but it probably means here “anything connected with religion” - admonition, precept, or doctrine. Pearls are precious stones found in shell-fish, chiefly in India, in the waters that surround Ceylon. They are used to denote anything especially precious, Revelation 17:4; Revelation 18:12-16; Matthew 13:45. In this place they are used to denote the doctrines of the gospel. “Dogs” signify people who spurn, oppose, and abuse that doctrine; people of special sourness and malignity of temper, who meet it like growling and quarrelsome curs, Philippians 3:2; 2 Peter 2:22; Revelation 22:15. “Swine” denote those who would trample the precepts underfoot; people of impurity of life; those who are corrupt, polluted, profane, obscene, and sensual; those who would not know the value of the gospel, and who would tread it down as swine would pearls, 2 Peter 2:22; Proverbs 11:22. The meaning of this proverb, then, is, do not offer your doctrine to those violent and abusive people who would growl and curse you; nor to those especially debased and profligate who would not perceive its value, would trample it down, and would abuse you. This verse furnishes a beautiful instance of what has been called the “introverted parallelism.” The usual mode of poetry among the Hebrews, and a common mode of expression in proverbs and apothegms, was by the parallelism, where one member of a sentence answered to another, or expressed substantially the same sense with some addition or modification. See the Introduction to the Book of Job. Sometimes this was alternate, and sometimes it was introverted - where the first and fourth lines would correspond, and the second and third. This is the case here. The dogs would tear, and not the swine; the swine would trample the pearls under their feet, and not the dogs. It may be thus expressed:
Give not that which is holy unto the dogs,
Neither cast ye your pearls before swine,
Lest they (that is, the swine) trample them under their feet,
And turn again (that is, the dogs) and rend you.

All things whatsoever ... - This command has been usually called the “Saviour’s golden rule,” a name given to it on account of its great value. All that you “expect” or “desire” of others in similar circumstances, do to them. Act not from selfishness or injustice, but put yourself in the place of the other, and ask what you would expect of him. This would make you impartial, candid, and just. It would destroy avarice, envy, treachery, unkindness, slander, theft, adultery, and murder. It has been well said that this law is what the balance-wheel is to machinery. It would prevent all irregularity of movement in the moral world, as that does in a steam-engine. It is easily applied, its justice is seen by all people, and all must acknowledge its force and value.
This is the law and the prophets - That is, this is the sum or substance of the Old Testament. It is nowhere found in so many words, but if is a summary expression of all that the law required. The sentiment was in use among the Jews. Hillel, an ancient Rabbi, said to a man who wished to become a proselyte, and who asked him to teach him the whole law, “Whatever is hateful to you, do not do to another.” Something of the same sentiment was found among the ancient Greeks and Romans, and is found in the writings of Confucius.

False prophets - The word prophet originally means one who foretells future events. As prophets, however, were commonly regarded as public instructors on the subject of religion, the word came to denote all who were religious teachers. See the notes at Romans 12:6. In this sense it is probably used here. A false prophet is a teacher of incorrect doctrine, or one falsely and unjustly laying claims to divine inspiration. It probably had reference to the false teachers then among the Jews.
Who come in sheep’s clothing - The sheep is an emblem of innocence, sincerity, and harmlessness. To come in sheep’s clothing is to assume the appearance of sanctity and innocence, when the heart is evil.
Ravening wolves - Rapacious; voraciously devouring; hungry even to rage. Applied to the false teachers, it means that they assumed the appearance of holiness in order that they might the more readily get the property of the people. They were full of extortion and excess. See Matthew 23:25.

Ye shall know them by their fruits - The Saviour gives the proper test of their character. People do not judge of a tree by its leaves, or bark, or flowers, but by the fruit which it bears. The flowers may be beautiful and fragrant, the foliage thick and green; but these are merely ornamental. It is the “fruit” that is of chief service to man; and he forms his opinion of the nature and value of the tree by that fruit. So of pretensions to religion. The profession may be fair; but the “conduct” - the fruit - is to determine the nature of the principles.

A corrupt tree - The word “corrupt” here does not signify, as our translation would seem to indicate, that the tree “had been” good, but had become “vitiated;” but that it was a tree of a useless character, of a nature that produced nothing beneficial.

Not every one that saith ... - The Saviour goes on to say that many, on the ground of a mere profession such as he had just referred to, would claim admittance into his kingdom. Many would plead that they had done miracles, and preached or prophesied much, and on the ground of that would demand an entrance into heaven. The power of working miracles had no necessary connection with piety. God may as well, if he chooses, give the power of raising the dead to a wicked man, as the skill of healing to a wicked physician. A miracle is a display “of his own power” through the medium of another. An act of healing the sick is also a display of “his power” through the agency of another. In neither of these cases is there any necessary connection with moral character. So of preaching or prophesying. God may use the agency of a man of talents, though not pious, to carry forward His purposes. Saving power on the mind is the work of God, and he may convey it by any agency which he chooses. Accordingly, many may be found in the day of judgment who may have been endowed with powers of prophecy or miracle, as Balaam or the magicians of Egypt; in the same way as many people of distinguished talents may be found, yet destitute of piety, and who will be shut out of his kingdom. See Matthew 7:21; 1 Corinthians 1:26; 1 Corinthians 13:1-3. In this last place Paul says that, though he spoke with the tongue of angels, and had the gift of prophecy, and could remove mountains, and had nor charity or love, all would be of no avail. See the notes at 1 Corinthians 13:1-3.

In that day - That is, in the last day, the day of judgment; the time when the principles of all pretenders to prophecy and piety shall be tried.

Profess unto them - Say unto them; plainly declare.
I never knew you - That is, I never approved of your conduct; never loved you; never regarded you as my friends. See Psalms 1:6; 2 Timothy 2:19; 1 Corinthians 8:3. This proves that, with all their pretensions, they had never been true followers of Christ. Jesus will not then say to false prophets and false professors of religion that he had once known them and then rejected them; that they had been once Christians and then had fallen away; that they had been pardoned and then had apostatized but that he had never known them - they had never been true christians. Whatever might have been their pretended joys, their raptures, their hopes, their self-confidence, their visions, their zeal, they had never been regarded by the Saviour as his true friends. I do not know of a more decided proof that Christians do not fall from grace than this text. It settles the question; and proves that whatever else such people had, they never had any true religion. See 1 John 2:19.