(3) باب إزالة النجاسة وبيانها
In the version of Muslim:
"I used to scrape it (the semen) off the garment of Allah's Messenger (ﷺ) and then he offered prayer with it.
Reference: Bulugh al-Maram 28
In-book reference: Book 1, Hadith 32
English translation: Book 1, Hadith 31