Musnad Abu Ya'la al-Mawsili 155:110

And from Abu Salamah, he said: I saw Abu Hurairah prostrate in "When the sky has split" (Surah al-Inshiqaq). When he finished, I said to him: "You prostrated in a Surah in which [people] do not prostrate." He said: "I saw the Messenger of Allah, may Allah bless him and grant him peace, prostrate in it."