Job 9:20

If I justify myself, mine own mouth shall condemn me: if I say, I am perfect, it shall also prove me perverse.

The book of Job is the oldest of the poetical books that have come down, divided into four parts: the prose prologue in chapters 1 and 2, the debate between Job and his three friends on the subject of his afflictions in chapters 4 to 31 in three circles of speeches on the part of each, the speeches of Elihu in chapters 32 to 37, the speeches of the Lord out of the storm-cloud, and the epilogue in chapter 42:7-17, with this verse standing in the second part. It belongs to the portion that presents the great problems that have perplexed humanity through all ages, overruling providence and sin and suffering. In its immediate setting God is disciplining Job and bringing him through the fire of affliction while his three friends charge him with sin and declare his sufferings are because of sin, showing how humanity is prone to misjudge its fellows in suffering in the same way. The speech here is Job's answer to Bildad.

The friends' claims about good and evil were generally true but were misapplied to Job, showing that suffering does not prove that a person is under God's displeasure. Job knew his own integrity but could not use his innocence to explain God's dealings with him, and he did not foolishly accuse God. The verse is an appeal for humility: to try to justify oneself brings condemnation from one's own words, and to say one is perfect proves one perverse.

A person cannot establish his own innocence before God, so human works cannot be the ground of justification. A profession of perfection may itself reveal failure to see one's own condition, and Job, though called perfect by God, did not claim awareness of that attainment but recognized he could not justify himself before God.