Sahih Al Bukhari Hadith Number 768

Narrated Abu Rafi`: Once I prayed the `Isha’ prayer with Abu Huraira and he recited, “Idha s-samaa’u n-shaqqat” (84) and prostrated. I said, “What is that?” He said, “I prostrated behind Abul-Qasim, (the Prophet) (when he recited that Sura) and I will go on doing it till I meet him.”

10  Call to Prayers (Adhaan)
Hadith number 768
Volume no 1
Chapter: 101 (To recite in the ‘Isha prayer, with As-Sajda(prostration)