It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that a woman asked the Messenger of Allah (peace and blessings be upon him), saying: "O Messenger of Allah, I suffer from prolonged bleeding (istihadah) and I do not become pure; should I abandon the prayer?" He (peace and blessings be upon him) said: "No, but leave the prayer for as many days and nights as you used to menstruate, and their equivalent in the month; then perform ghusl, bind yourself with a cloth and pray."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20219