Sunan Abi Dawud

Narrated Abu Rafi':I offered the night prayer behind Abu Hurairah. He recited Surah Inshiqaq (""When the sky is rent asunder"") and prostrated himself. I asked him: What is this prostration ? He replied: I prostrated myself on account of this (surah) behind Abu al-Qasim (i.e. the Prophet). I shall continue prostrating on account of this till I meet him