It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that in the time of the Prophet (peace and blessings be upon him) a woman bled continuously. Sayyidah Umm Salamah (may Allah be pleased with her) said to her: Ask the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) said: "Let her look at the number of days and nights in the month during which she used to menstruate before, and abandon the prayer for that many days; then take a ritual bath, bind yourself with a cloth and pray."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1579