Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 294
Narated By 'Aisha, Ummul Mu'minin : A woman had a prolonged flow of blood in the time of the Apostle of Allah (pbuh). She was commanded to advance the afternoon prayer and delay the noon prayer, and to take a bath for them only once; and to delay the sunset prayer and advance the night prayer and to take a bath only once for them; and to take a bath separately for the dawn prayer.
I (Shu'bah) asked Abdur Rahman: (Is it) from the Prophet (pbuh)? I do not report to you anything except from the Prophet (pbuh).