When translating papers from non-English to English, should the sources be translated to English as well? When translating research papers from Arabic to English, should I translate the Arabic sources (book titles, etc.) to English, or should I leave them in Arabic?
I will argue that, for maximum usefulness to your readers, you should do both.
In other words, put both the original and the translation in the entry, e.g. either:


  English citation (original: Arabic citation)


or


  Arabic citation (translation: English citation)


I don't see either of these are being particularly dominant over the other.  Both, however, allow one to both trace the original and know what it is without speaking Arabic.

Note that I would believe this answer should apply to any translation between languages.  It is most critical, however, when the writing systems are incompatible, e.g., Arabic, Roman-character languages, South Asian languages, Chinese, etc.