Abdullah bin Mubarak عبد الله بن المبارك · The Book of Menstruation and Istihadah

"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."

"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 it has passed, then wash the blood from yourself and pray.'"