Sunan an Nasai
351
Sahih+2

It was narrated that 'Aishah said:"Umm Habibah bint Jahsh asked the Messenger of Allah (ﷺ): 'O Messenger of Allah, I suffer from Istihadah.' He said: 'That is a vein, so perform Ghusl, then pray.' And she used to perform Ghusl for each prayer

SahihAbu Ghuddah
SahihAl-Albani