Context helps quite a bit for this question. The full paragraph reads (to a slightly broader degree:
Plagiarism also became a significant idea exercising the critics' concerns. The works of al-Mutanabbi were particularly studied with this concern. He was considered by many the greatest of all Arab poets but his own arrogant self-regard for his abilities did not endear him to other writers and they looked for a source for his verse.
This is talking about plagiarism. What it seems to be implying is that al-Mutanabbi was such an arrogant person about his own abilities that the other writers possibly disliked him and wanted to find proof that he hadn't actually written the poetry he claimed to have written. So, looked for a source for his work means they were researching old texts trying to find the poems he claimed to have written.
This is the equivalent of a modern professor Googling the content of an essay you turn in to check if you actually wrote it yourself or copied it from some other source.
Part B actually appears to be quite different on the Wikipedia page than what you quote:
Just as there were collections of facts written about many different subjects, numerous collections detailing every possible rhetorical figure used in literature emerged as well as how to write guides.
This, I think, is just a poorly written, overcomplicated example of why Wikipedia isn't the best source for serious research.
This sentence starts by saying:
Collections of facts were written about many different subjects.
This is just a simple statement. It may not even relate to Arabic Literature alone... there are thousands of reference books out there on many topics. This can honestly probably be removed from the sentence.
In the rest of the sentence, the sentence lists a couple of types of collections of fact that relate to the subject of the article:
Collections about rhetorical figures used in literature
Guides about how to write in this style.
The problem with this sentence is that emerged got plopped in a very ... nonsensical spot.
Emerged is the verb here. The word choice is used appropriately but the placement is very unusual. as well as is transitively tying emerged to both of the parts of the statement:
The definition of emerged being used here is:
to become known or apparent
Though, in this case, it could possibly have the meaning came into common use or came into existence.
I've been attempting to rewrite the sentence and failing because the meaning of the sentence is not clear, so rewriting it has a tendency to change its meaning.