Abdur Rahman bin al-Qasim عبد الرحمن بن القاسم بن محمد بن أبي بكر · The Book of Menstruation and Istihadah

It was narrated from 'Aishah that a woman who suffered from Istihadah at the time of the Messenger of Allah (ﷺ) was told that it was a stubborn vein (i.e., one that would not stop bleeding). She was told to delay Zuhr and bring 'Asr forward, and to perform one Ghusl for both, and to delay Maghrib and bring 'Isha' forward, and to perform one Ghusl for both, and she would perform one Ghusl for Subh.

"I said to the Prophet (ﷺ) that I was suffering from Istihadah. He said: 'Do not pray during the days of your period, then perform Ghusl and delay Zuhr and bring Maghrib and bring 'Isha' forward and pray them together, and perform Ghusl for Fajr."

"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…