Translation:

52. And thus have We by Our command sent inspiration to thee: thou knowest not (before) what was Revelation and what was Faith; but We have made the (Qur'an) a Light wherewith We guide such of Our servants as We will; and verily thou dost guide (men) to the Straight Way

Notes (Tafseer)

4601. Before the receipt of his mission in his fortieth year, the holy Prophet, though a man of steadfast virtue and purity and unflinching in his search for Truth, was yet unacquainted with Revelation in the highest sense of the term and with the certainty that comes from perfected Faith, or realised nearness to Allah. Ruh, which I have here translated Inspiration has also been understood by some Commentators to refer to the angel Gabriel, the vehicle of Revelation. The Light of the Qur-an made all things clear to man, and to the world.

4602. The Qur-an and the inspired Prophet who proclaimed it, are here identified. They were a Guide to men, showing the Straight Way. This Way is described in various ways: for example, see i. 6, and n. 22; xviii. 1-2, and notes 2326-27; and xc. 11-18.