Students of Arabic are usually amused to learn that the Arabic word for "grass" – the sort that grows in cracks between the paving stones – is hashish. The English word “cannabis”, meanwhile, comes from the Arabic qinnab al-hind - literally meaning “Indian hemp”. Some also claim the word “assassin” is derived from “hashish” via an Ismaili sect known as the Hashashin(though that is disputed).

Anyway, the Tabsir blog has discovered an old book (1971) called The Herb: Hashish versus Medieval Muslim Society, by 
Franz Rosenthal, which “sorts through legal, medical and literary sources to provide a historical overview of the issues surrounding the use of hashish”.

As its use spread in the 12th and 13th centuries opinion became divided. Users, the book says, “felt that they could be at peace with their Muslim conscience. Where pure hedonism was not a sufficient excuse for indulgence, the drug could also be claimed to open up new spiritual and intellectual vistas and thus to contribute to an otherwise unobtainable sharpening of the religious experience, thereby bringing mankind closer to what was imagined to be its essential goal.”

This did not please Ibn Taymiyyah (1263-1328), the religious scholar much admired by salafis and jihadists today:

“Hashish,” Ibn Taymiyah says, “requires the haddpenalty more than wine. The harm a hashish eater causes to his own person is greater than that caused by wine. On the other hand, the harm a windedrinker causes to the people is greater (in view of the quarrels and the like provoked by alcohol). However, in these times, because the consumption of hashish is spreading, the harm coming from it to the people is greater than that of wine.”

The book is out of print but most of it can be read at
Google Books.