Mishkat al-Masabih #516

‘A'isha told of Fatima daughter of Abu Hubaish coming to the Prophet and saying, “I am a woman whose blood keeps flowing, and I am never purified; Shall I therefore abandon prayer?” He replied, “No that is only a vein and is not menstruation; so when your menstrua­ tion comes on abandon prayer, and when it ends wash the blood from yourself and then pray.” (Bukhari and Muslim.)