Can I quote something directly in a foreign language?
Reasons why you might want to include the original:


There are issues related to the precise wording and terms used in the original, which you pick up and elaborate on.
There is no reliable translation available, i.e. no published article contains the quote you would like to refer to. In this case, I would translate the quote myself and add a footnote along the lines of "original text" [source] (translated by this article's author).
Understanding the language the original is in is expected from the reader, e.g. in an article about the particular language. No need to include the translation in that case.


In any other case, I would stick to the translated version solely (and attribute it to its source as usual).