For you ask, ‘What does it profit me, and what benefit do I gain apart from sin?’
We have here, I. The bad words which Elihu charges upon Job, Job 35:2, Job 35:3. To evince the badness of them he appeals to Job himself, and his own sober thoughts, in the reflection: Thinkest thou this to be right? This intimates Elihu's confidence that the reproof he now gave was just, for he could refer the judgment of it even to Job himself.
Commenting on Job 35:1-8
I will answer thee, and thy companions with thee. Meaning not his three friends, as the Septuagint version expresses it; for they were not on the side of Job, and of the same sentiment with him, but rather on the side of Elihu; especially Eliphaz, who expresses much the same sentiment he does, Job 22:2; but all that were of the same mind with Job...
Rather, explanatory of "this" in Job 35:2, "That thou sayest (to thyself, as if a distinct person) What advantage is it (thy integrity) to thee? What profit have I (by integrity) more than (I should have) by my sin?" that is, more than if I had sinned (Job 34:9).