(10) باب الحيض
Narrated Umm Salamah (RAA):
During the lifetime of the Prophet (Peace be upon him) the women having bleeding after delivery (postnatal or puerperal blood) would refrain (from prayer) for forty days.[Reported by Al-Khamsa except An-Nasa'i, and the version is that of Abu Da'ud].
Reference: Bulugh al-Maram 150
In-book reference: Book 1, Hadith 179
English translation: Book 1, Hadith 161