(6) باب الْفَرْقِ بَيْنَ دَمِ الْحَيْضِ وَالاِسْتِحَاضَةِ
It was narrated from 'Aishah that the daughter of Abu Hubaish said:
"O Messenger of Allah, I do not become pure, so should I stop praying? He said: "no, that is a vein." - (One of the narrators) Khalid said, in what I read from him - "and it is not menstruation, so when your period comes, stop praying, and when it goes, wash the blood from yourself and pray."
Reference: Sunan an-Nasa'i 367
In-book reference: Book 3, Hadith 19
English translation: Vol. 1, Book 3, Hadith 367