Sunan at-Tirmidhi (Jami-al-Tirmidhi), Chapter: Taharah (Purification)

reported that Sayyidah Fatimah bint Abu Hubaysh (RA) came to the Prophet (SAW) and said, "O Messenger of Allah! I am a woman who gets istihadah (a continuous flow of blood) and I am never purified. Shall I stop offering Salah?" He said, "No! That is only a vein (that bleeds and is no part of the womb and there are other reasons for that). It is not menstruation. When you have menses, stop Praying and when they are over wash the blood from your body and offer Salah." [Ahmed24577, Bukhari 228, Muslim 333, Nisai 359, Ibn e Majah 621]