Chapter 18

Bildad speaks a second time:

He seems a little miffed that Job despises the advice of his friends.

5 "Indeed, the light of the wicked is put out, and the flame of his fire does not shine. [Job 18:5 ESV]

Bildad continues as before, that those who suffer like Job have some problem.  Bildad is referring back to Jobs statement in 17:12 I think, where he said:

12 They make night into day: 'The light,' they say, 'is near to the darkness.' [Job 17:12 ESV]

Bildad's speech this time is less kindly, and includes a long list of the consequences that evil men suffer.  Many of the things he talks about are the things of which Job has just complained.  He concludes with this:

21 Surely such are the dwellings of the unrighteous, such is the place of him who knows not God." [Job 18:21 ESV]

He refers here to the fact that most of the well known consequences he has just listed apply to Job's current condition.  He is saying outright that Job has no knowledge or understanding of God at all.  How can Job be suffering precisely the fate - the well known and universally recognized punishments that visit the ungodly - and sit there denying that he has sinned?  Bildad is not mincing words here.  He is trying to "slap Job into reality".