Sunan Abu Dawud
297
Sahih+3

Narrated Grandfather of Adi ibn Thabit ?: The Prophet (ﷺ) said about the woman having a prolonged flow of blood: She should abandon prayer during her menstrual period: then she should take a bath and pray. She should perform ablution for every prayer. Abu Dawud said: 'Uthman added: She should keep fast and pray

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid