Job 9:3 (ESV)

3 If one wished to contend with him, one could not answer him once in a thousand times.

In an ancient Near Eastern dispute, one party would make statements and the other party would try to refute those statements one by one. Job says that a dispute with God would be impossible, since the two parties would be wholly unequal. A man would not even be able to answer one out of a thousand statements made by God.