Nafie' نافع مولى ابن عمر · The Book of Menstruation and Istihadah

"A woman asked the Prophet (ﷺ): 'I suffer from Istihadah and I never become pure; should I stop praying?' He said: 'No. Stop praying for the number of days and nights that you used to menstruate, then perform Ghusl, wrap a cloth around yourself, and pray.'"

"Let her count the number of nights and days that she used to menstruate each month before this happened to her, and let her stop praying for that period of time each month. Then when that is over let her perform Ghusl, then wrap a cloth around herself, and pray."