Sahih Muslim, Chapter: Faith (Kitab Al Iman)

that he heard the Messenger of Allah (may peace be upon him) says: The wahi was intermitted for me for a small span of time and while I was walking, and then the hadith like the one narrated by Yunus was transmitted but with the exception of these words: I was terror-stricken till I fell on the ground. Abu Salama said: Defilement means idols. After this the revelation was speeded up and followed rapidly.