Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 342
Abdullah b. Shaqiq reported: I said to Abu Dharr: Had I seen the Messenger of Allah, I would have asked him. He (Abu Dharr) said: What is that thing that you wanted to inquire of him? He said: I wanted to ask him whether he had seen his Lord. Abu Dharr said: I, in fact, inquired of him, and he replied: I saw Light.