The following excerpt is taken from “The Message of the Quran” by Muhammad Asad pg. 954-955:
And it is not given to mortal man that God should speak unto him otherwise than through sudden 52 inspiration, or [by a voice, as it were,] from behind a veil, or by sending an apostle to reveal, by His leave, whatever He wills [to reveal]: 53 for, verily, He is exalted, wise.
Note 52: This is the primary meaning of wahy, a term which combines the concepts of suddenness and inner illumination (Raghib); in the usage of the Qur’an, it is often, though by no means always, synonymous with “revelation”. – The above passage connects with the first paragraph of verse 48, which speaks of the divine message entrusted to the Prophet.
Note 53: Cf. 53:10
The following is from page 1038 of the same book:
And thus did [God] reveal unto His servant whatever He deemed right to reveal,6
Lit., “whatever He revealed”: an allusion to the exceptional manifestation of the angel “in his true shape and nature” as well as to the contents of divine revelation as such. In its deeper sense the above phrase implies that even to His chosen prophets God does not entirely unveil the ultimate mysteries of existence, of life and death, of the purpose for which He has created the universe, or of the nature of the universe itself.