Imam Maalik مالك بن أنس بن مالك بن أبي عامر · The Book of Menstruation and Istihadah

"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."

Fatimah bint Abi Hubaish said to the Messenger of Allah (ﷺ): "O Messenger of Allah (ﷺ), I do not become pure. Should I stop praying?" The Messenger of Allah (ﷺ) said: "That is a vein and is not menstruation. When your period comes, stop praying, and when the same amount of time as your regular period has passed, then wash the blood from yourself and pray."

"The Messenger of Allah (ﷺ) used to put his head out of the Masjid while he was performing I'tikaf, and I would wash it, while I was menstruating."

"Umm 'Atiyah would never mention the Messenger of Allah (ﷺ) without saying: 'May my father be ransomed for him.' I said: 'Did you hear the Messenger of Allah (ﷺ) say such and such?' And she said: 'Yes, may my father be ransomed for him.' He said: 'Let the mature girls, virgins staying in seclusion, and menstruating woman go out and witness the good occasions and the supplications of the Muslims, but let the menstruating women keep away from the prayer…