Surah 17. Al-Israa, Ayah 86

Lit., "to be thy guardian against [or "before"] Us" - i.e., "to provide thee with other means of guidance": an allusion to the fact that divine guidance is the only source of ethics in the absolute sense of this word. The "taking away" of revelation denotes its alienation from the hearts and the memory of men, as well as its disappearance in written form.

Even the spiritual knowledge that comes to us comes because of the favour and mercy of Allah. If He were to withhold it, who can call Him in question?