Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1980
Abu Juraij narrated this hadith with the same chain of transmitters (but with the addition of these words):" It was for a long duration that he (the Holy Prophet) observed qiyam and he would then observe ruku'. (The narrator also added) I (Asma') looked at a woman who was older than I, and at another who was weaker than I.