But if ye have respect to persons, ye commit sin - You transgress the plain law of God, and do wrong. See the references on James 2:1.
And are convinced of the law as transgressors - Greek “By the law.” The word convinced is now used in a somewhat different sense from what it was formerly. It now commonly refers to the impression made on a man’s mind by showing him the truth of a thing which before was doubted, or in respect to which the evidence was not clear. A man who doubted the truth of a report or a proposition may be convinced or satisfied of its truth; a man who has done wrong, though he supposed he was doing what was proper, may be convinced of his error. So a man may be convinced that he is a sinner, though before he had no belief of it, and no concern about it; and this may produce in his mind the feeling which is technically known as conviction, producing deep distress and anguish. See the notes at John 16:8. Here, however, the word does not refer so much to the effect produced on the mind itself, as to the fact that the law would hold such an one to be guilty; that is, the law pronounces what is done to be wrong. Whether they would be personally convinced of it, and troubled about it as convicted sinners, would be a different question, and one to which the apostle does not refer; for his object is not to show that they would be troubled about it, but to show that the law of God condemned this course, and would hold them to be guilty. The argument here is not from the personal distress which this course would produce in their own minds, but from the fact that the law of God condemned it.