Albert Barnes Commentary Job 35:16

"Therefore doth Job open his mouth in vanity; He multiplieth words without knowledge." — Job 35:16 (ASV)

Therefore— In view of all that Elihu had now said, he came to the conclusion that the views of Job were erroneous, and that he had no just cause of complaint. He had suffered no more than he had deserved; he might have obtained a release or mitigation if he had applied to God; and the government of God was just, and was every way worthy of confidence. The remarks of Job, therefore, complaining of the severity of his sufferings and of the government of God, were not based on knowledge, and had in fact no solid foundation.