The Book of Purification
1/138. Chapter:
The Difference Between Menstrual Blood And Non-Menstrual Bleeding
Sunan an-Nasai
أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنْ مُحَمَّدٍ، - وَهُوَ ابْنُ عَمْرِو بْنِ عَلْقَمَةَ بْنِ وَقَّاصٍ - عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ فَاطِمَةَ بِنْتِ أَبِي حُبَيْشٍ، أَنَّهَا كَانَتْ تُسْتَحَاضُ فَقَالَ لَهَا رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا كَانَ دَمُ الْحَيْضِ - فَإِنَّهُ دَمٌ أَسْوَدُ يُعْرَفُ - فَأَمْسِكِي عَنِ الصَّلاَةِ فَإِذَا كَانَ الآخَرُ فَتَوَضَّئِي فَإِنَّمَا هُوَ عِرْقٌ " .
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."
Reference : Sunan an-Nasa'i 215In-book reference : Book 1, Hadith 216English translation : Vol. 1, Book 1, Hadith 216