And why seest thou the straw? He expressly touches upon a fault, which is usually found in hypocrites. While they are too quick-sighted in discerning the faults of others, and employ not only severe, but intentionally exaggerated, language in describing them, they throw their own sins behind their back, or are so ingenious in finding apologies for them, that they wish to be held excusable even in very gross offenses. Christ therefore reproves both evils: the excessive sagacity, which arises from a defect of charity, when we sift too closely the faults of brethren, and the indulgence by which we defend and cherish our own sins.

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.

And why beholdest thou the mote - Καρφος might be translated the splinter: for splinter bears some analogy to beam, but mote does not. I should prefer this word (which has been adopted by some learned men) on the authority of Hesychius, who is a host in such matters; Καρφος, κεραια ξυλου λεπτη, Karphos is a thin piece of wood, a splinter. It often happens that the faults which we consider as of the first enormity in others are, to our own iniquities, as a chip is, when compared to a large beam. On one side, self-love blinds us to ourselves; and, on the other, envy and malice give us piercing eyes in respect of others. When we shall have as much zeal to correct ourselves, as we have inclination to reprove and correct others, we shall know our own defects better than now we know those of our neighbor. There is a caution very similar to this of our Lord given by a heathen: -
Cum tua praevideas oculis mala lippus inunctis:
Cur in amicorum vitiis tam cernis acutum,
Quam aut aquila, aut serpens Epidaurius?
Hor. Sat. lib. 1. sat. 3. l. 25-27
"When you can so readily overlook your own wickedness, why are you more clear-sighted than the eagle or serpent of Epidaurus, in spying out the failings of your friends?"
But the saying was very common among the Jews, as may be seen in Lightfoot.

And why beholdest thou the mote that is in thy brother's eye?.... By "mote" is meant, any little bit of straw, or small splinter of wood, that flies into the eye, and does it damage, hinders its sight, and gives it pain; and designs little sins, comparatively speaking, such as youthful follies, human frailties, and infirmities, inadvertencies and imprudencies; which may be said to be light faults, in comparison of others: and though not to be vindicated, nor continued in, yet not to be severely looked upon and chastised. To scrutinize diligently into, aggravate, dwell upon, and sharply reprove the lighter faults of others, is a conduct, which is here inveighed against, and condemned by Christ; and more especially, when it may be said with the greatest truth and justice to such,
but considerest not the beam that is in thine own eye: by the "beam" is meant, greater sins, grosser abominations, and such as were more peculiar to the Pharisees; as pride, arrogance, a vain opinion of themselves, confidence in their own righteousness, hypocrisy, covetousness, and iniquity; things they did not advert to in themselves, when they loudly exclaimed against lesser evils in others. Such men must be of all persons inexcusable, who condemn that in others, which either they themselves do, or what is abundantly worse.

And why beholdest thou the mote--"splinter," here very well rendered "mote," denoting any small fault.
that is in thy brother's eye, but considerest not the beam that is in thine own eye?--denoting the much greater fault which we overlook in ourselves.

Why beholdest thou the mote that is in thy brother's eye? The Lord uses a figure to show the absurdity of judging severely the faults of others, while we have greater ones. The term translated "mote" means a little splinter, while the beam is something very large.

In particular, why do you open your eyes to any fault of your brother, while you yourself are guilty of a much greater? The mote - The word properly signifies a splinter or shiver of wood. This and a beam, its opposite, were proverbially used by the Jews, to denote, the one, small infirmities, the other, gross, palpable faults. Luke 6:41.