COMMENTARY on 17:85
A. Yusuf Ali:

Translation:
They ask you concerning the Spirit (of inspiration). 2285 Say: "The Spirit (cometh) by command of my Lord: of knowledge it is only a little that is communicated to you, (O men!)"
Commentary:

2285  What is the nature of inspiration? Who brings it? Can it ask its Bringer questions? Can we ask anything which we wish? These are the sort of questions always asked when inspiration is called in question. The answer is given here. Inspiration is one of those high spiritual mysteries which cannot be explained in the terms of everyday human experience. It is spiritual. The Spirit (Gabriel) does not come of his own will. He conies by the command of Allah, and reveals what Allah commands him to reveal. Of the sum total of true spiritual knowledge what a small part it is that ordinary mortals can understand! They can be only given that which they can understand, however dimly. We are not in a position to ask anything that we wish. If we did so, it would only make us look foolish, for the guidance comes from Allah's Wisdom, not from our worldly knowledge.

 

Muhammad Asad:

Translation:
AND THEY will ask thee about [the nature of] divine inspiration. 101 Say: "This inspiration [comes] at my Sustainer's behest; and [you cannot understand its nature, O men, since] you have been granted very little of [real] knowledge."
Commentary:
101  For this interpretation of the term ruh, see surah 16, note 2. Some commentators are of the opinion that it refers here, specifically, to the revelation of the Qur'an; others understand by it the "soul", in particular the soul of man. This latter interpretation is, however, unconvincing inasmuch as the preceding as well as the subsequent verses relate explicitly to the Qur'an and, hence, to the phenomenon of divine revelation.