If he will contend with him, he cannot answer him one of a thousand.
If he (God) will contend, with him - literally, 'deign to enter into judgment:' 'If it were His good, pleasure х yachpots (H2654)] to enter into judgment with him' - i:e., to argue with man as to the rights of the question at issue between Him and man.
He cannot answer. He (man) could not and would not dare to answer in defense of his cause to one of the thousand questions of God, from awe of his Majesty. How, then, can man maintain his justice before God? (cf. Job 9:15). This was what, in fact, took place in the end: God asked many questions of Job, to not one of which Job could give an answer, (Job 38:1, etc.)