Yahya related to me from Malik from Yahya ibn Said that Said ibnal-Musayyab was asked, "What do you say about someone who is afflictedby a nose-bleed which does not stop? "Malik said that Yahya ibn Saidsaid that Said ibn al Musayyab said, "I say that he should signal withhis head." (i.e. instead of doing sajda or ruku.)Yahya saidthat Malik said, "That is what I like most out of what I have heardabout the matter."
USC-MSA web (English) reference: Book 2, Hadith 54
Arabic reference: Book 2, Hadith 84