It was narrated from Fatimah bint Qais from Banu Asad Quraish that she came to the Prophet (ﷺ) and mentioned that she suffered from Istihadah. She said that he said to her:"That is a vein, so when the time of menstruation comes, stop praying, and when it goes, take your bath and wash the blood from yourself then pray

English translation · Sunan an-Nasa'i