Verse 20. - If I justify myself, mine own mouth shall condemn me. Since he could not wholly justify himself. "All men have sinned, and come short of the glory of God" (Romans 3:23). Job has already admitted the utterance of "rash words" (Job 6:3), and, at least hypothetically, that he "has sinned" (Job 7:20), and needs "pardon" for his "transgression" (Job 7:24). Job, if he tried to "justify himself," would have to acknowledge such shortcomings, such imperfections, such sins - at any rate, of infirmity - as would make his attempted justification a real self-condemnation. If I say, I am perfect, it shall also prove me perverse; rather, even were I perfect it (i.e. my mouth) would prove me perverse; i.e. supposing I were actually perfect, and tried to prove it, my speech would be so hesitating and confused, that I should only seem to be perverse.

9:14-21 Job is still righteous in his own eyes, ch. 32:1, and this answer, though it sets forth the power and majesty of God, implies that the question between the afflicted and the Lord of providence, is a question of might, and not of right; and we begin to discover the evil fruits of pride and of a self-righteous spirit. Job begins to manifest a disposition to condemn God, that he may justify himself, for which he is afterwards reproved. Still Job knew so much of himself, that he durst not stand a trial. If we say, We have no sin, we not only deceive ourselves, but we affront God; for we sin in saying so, and give the lie to the Scripture. But Job reflected on God's goodness and justice in saying his affliction was without cause.If I justify myself,.... Seek for justification by his own righteousness, trust in himself that he was righteous, say that he was so, and pronounce himself a righteous man, what would it signify?

mine own mouth shall condemn me; the words of it being sinful, vain, idle, and frothy; and if a man is to be justified, and condemned by his words, he may be sure of the latter: indeed, "if any man offend not in word, the same is a perfect man", James 3:2; but let a man be as careful as he can, and keep ever such a guard upon his lips, such is the imperfection of human nature, that, though a Moses, he will speak unadvisedly with his lips, at one time or another, and in many things will offend; which would be his condemnation, if there was no other way to secure from it; nay, for a sinful man to justify himself, or to say that he is a righteous man by his own righteousness, and insist upon this before God, if he is tried upon it he must be condemned; yea, saying he is so is a falsehood, abominable to God, and enough to condemn him; and besides, a man that knows himself, as Job did, must be conscious of much sin within him, however externally righteous he may be before men; so that, should he say he was righteous, his conscience would speak, or cause his mouth to speak and contradict and condemn him:

if I say, I am perfect; not in an evangelical sense, as he was; but in a legal sense, so as to be free from sin, which no man that is perfect in a Gospel sense is; as Noah, Jacob, David, and others, who were so, yet not without sin; if therefore a man should assert this, he would not say that which was right, but what was perverse, as might be proved:

it shall also prove me perverse; to be a wicked man; either he, God, shall prove, or it, his mouth, as in the preceding clause; for to say this is to tell a lie, which to do is perverseness, see 1 John 1:8.