It was narrated from Ibn 'Abbas, from Maimunah the wife of the Prophet, that :
the Prophet performed ablution with the water left over after she had taken a bath to cleanse herself from sexual impurity. (JA)
English reference (JA): Vol. 1, Book 1, Hadith 372 (JA)
Arabic reference (JA): Book 1, Hadith 402 (JA)