(9) باب غَسْلِ دَمِ الْمَحِيضِ
Narrated Asma' bint Abi Bakr:
A woman asked Allah's Messenger (ﷺ), "O Allah's Messenger (ﷺ)! What should we do, if the blood of menses falls on our clothes?" Allah's Messenger (ﷺ) replied, "If the blood of menses falls on the garment of anyone of you, she must take hold of the blood spot, rub it, and wash it with water and then pray in (with it).
Reference: Sahih al-Bukhari 307
In-book reference: Book 6, Hadith 12
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 6, Hadith 304