Job 9:3

If he will contend with him - God is so holy, and his law so strict, that if he will enter into judgment with his creatures, the most upright of them cannot be justified in his sight.

One of a thousand - Of a thousand offenses of which he may be accused he cannot vindicate himself even in one. How little that any man does, even in the way of righteousness, truth, and mercy, can stand the penetrating eye of a just and holy God, when all motives, feelings, and objects, come to be scrutinized in his sight, on this ground, no man living can be justified. O, how necessary to fallen, weak, miserable, imperfect and sinful man, is the doctrine of justification by faith, and sanctification through the Divine Spirit, by the sacrificial death and mediation of the Lord Jesus Christ!

If he will contend with him - That is, if God enters into a controversy with man. If he chooses to charge crime on him, and to hold him responsible for his deeds. The language here is taken from courts of justice, and means that if a trial were instituted, where God should submit charges, and the matter were left to adjudication, man could not answer the charges against him; compare the notes at Isaiah 41:1.

He cannot answer him one of a thousand - For one of a thousand of the sins charged on him. The word "thousand" here is used to denote the largest number, or all. A man who could not answer for one charge brought against him out of a thousand, must be held to be guilty; and the expression here is equivalent to saying that he could not answer him at all. It may also be implied that God has many charges against man. His sins are to be reckoned by thousands. They are numerous as his years, his months, his weeks, his days, his hours, his moments; numerous as his privileges, his deeds, and his thoughts. For not one of those sins can he answer. He can give no satisfactory account before an impartial tribunal for any of them. If so, how deeply guilty is man before God! How glorious that plan of justification by which he can be freed from this long list of offences, and treated as though he had not sinned.

9:3 One - One accusation among a thousand which God shall produce against him.