Ok, I'm awake now
The short answer for a biblical literalist (which I am not), is that the Bible is the inspired and innerant word of God, therefor it doesn't matter that it was Job or Isiah or whoever who actually put the words on paper, it was God that inspired them to do so and therefore the whole Bible is the word of God and when it is quoted, that is understood.
As I said, I'm not a biblical literalist, so I agree that context as well as authorship is very important when trying to understand what a particular passage says.
Since I believe you are actually refering to one of my posts
, I'll just say that I hope I sufficiently explained everything I wrote.
If not, feel free to ask or comment