It was narrated from Fatimah bint Abi Hubaish that she suffered from Istihadah and the Messenger of Allah (ﷺ) said to her:"If it is menstrual blood then it is blood that is black and recognizable, so stop praying, and if it is other than that then perform Wudu', for it is just a vein
Hadith No. 215
Sunan an Nasai
Gradings:
Abu Ghuddah:
Hasan Sahih
Al-Albani:
Hasan Sahih
Zubair Ali Zai:
Daif