They are not only unworthy of the smallest and most inconsiderable reward, but deserve to be wholly condemned, because they are always stained by many blemishes; and what have pollutions to do with the presence of God?

For if a man think himself to be something - see Galatians 5:26. This is designed, evidently, to be another reason why we should be kind and tender to those who have erred. It is, that even those who are most confident may fall. They who feel secure, and think it impossible that they should sin, are not safe. They may be wholly deceived, and may be nothing, when they have the highest estimate of themselves. They may themselves fall into sin, and have need of all the sympathy and kindness of their brethren.
When he is nothing - When he has no strength, and no moral worth. When he is not such as he apprehends, but is lifted up with vain self-conceit.
He deceiveth himself - He understands not his own character. "The worst part of the fraud falls on his own head" - Doddridge. He does not accomplish what he expected to do; and instead of acquiring reputation from others, as he expected, he renders himself contemptible in their sight.

If a man think himself to be something - i.e. To be a proper Christian man; when he is nothing; being destitute of that charity which beareth, hopeth, and endureth all things. See 1-Corinthians 13:1, etc. Those who suppose themselves to excel all others in piety, understanding, etc., while they are harsh, censorious, and overbearing, prove that they have not the charity that thinketh no evil; and in the sight of God are only as sounding brass and a tinkling cymbal. There are no people more censorious or uncharitable than those among some religious people who pretend to more light and a deeper communion with God. They are generally carried away with a sort of sublime, high sounding phraseology, which seems to argue a wonderfully deep acquaintance with Divine things; stripped of this, many of them are like Samson without his hair.

For if a man think himself to be something,.... Of himself; to have anything of himself, to do anything of himself, and of himself to attain to life and salvation:
when he is nothing: of himself; not even as a creature, but owes his being and preservation, and all the mercies of life, to another, even to God; has no grace nor gifts of himself, but what he has received, and can do no good thing, not think a good thought, or perform a good action, of himself, and much less of himself procure eternal life and salvation:
he deceiveth himself: and will find himself sadly mistaken, and wretchedly disappointed another day; or whoever thinks himself to be some famous and excellent person, to be something more, and better than others, of a more excellent nature, and of greater abilities, that he is free from sin, or at least holier than others, and not liable to fall as others, whom he looks upon with disdain and contempt, wanting that charity which the law, and new commandment of Christ, requires, when he is nothing but sin and vanity, he is destitute of the grace of God, he deceives himself and the truth is not in him. This the apostle says to depress pride, and a swelling conceit of themselves, and all uncharitable, rough, and severe usages of others. A saying like this the Jews have (y);
"whoever he is that is something, or thinks in himself that he is "something", it would be better for him if he had never been created.''
(y) Midrash Kohelet, fol. 79. 1.

Self-conceit, the chief hindrance to forbearance and sympathy towards our fellow men, must be laid aside.
something--possessed of some spiritual pre-eminence, so as to be exempt from the frailty of other men.
when he is nothing--The Greek is subjective: "Being, if he would come to himself, and look on the real fact, nothing" [ALFORD] (Galatians 6:2, Galatians 6:6; Romans 12:3; 1-Corinthians 8:2).
deceiveth himself--literally, "he mentally deceives himself." Compare James 1:26, "deceiveth his own heart."

If a man think, etc. If he thinks he is strong, needs no help, will never need sympathy, etc., he deceiveth himself.
But let every man prove his own work. Instead of commenting upon the weaknesses of others, let him test his own work. If his work stands the test, there he can rejoice in it alone, not because he is superior to another.
For every man shall bear his own burden. This seems at first to conflict with Galatians 6:2. The meaning of Galatians 6:2 is "Bear ye one another's burden of trial and suffering;" of Galatians 6:5, "Every one must bear his own burden of responsibility." The first is aiding to bear the burden of another's infirmities; the second is the burden of our account before God. The Greek had two different words for "burden" in the two verses. It is unfortunate that the Versions do not represent the difference by two words in the English.
Let him that is taught. Let those who are taught by the preachers and teachers sustain those who instruct them.

If any one think himself to be something - Above his brethren, or by any strength of his own. When he is nothing, he deceiveth himself - He alone will bear their burdens, who knows himself to be nothing.