The Book Pertaining to Piety and Softening of Hearts (Kitab Al-Zuhd wa Al-Raqa'iq)
Muslim :: Book 42 : Hadith 7146
It was reported that Abu Huraira used to say: Listen to me, inmate of the apartment; listen to me, inmate of the apartment, while 'A'isha (Allah be pleased with her) had been busy in observing prayer. As she finished prayer, she said to" Urwa: Did you hear his words? And this is how Allah's Messenger (may peace be upon him) used to utter (so distinctly) that if one intended to count (the words uttered) he would be able to do so.