Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1978
Asma' said: I came to 'A'isha when the people were standing (in prayer) and she was also praying. I said: What is this excitement of the people for? And the rest of the hadith was narrated like one, (narrated above). 'Urwa said: Do not say Kasafat-ush-Shamsu, but say Khasafat-ush-Shamsu.