Yahya related to me from Malik from Yahya ibn Said that he waslistening to Said ibn al-Musayyab and a man questioned him saying, "Idiscover a liquid when I am praying. Should I leave?"Saidibn al-Musayyab said to him, "Even if it were to flow on my leg Iwould not leave until I had finished the prayer."
USC-MSA web (English) reference: Book 2, Hadith 58
Arabic reference: Book 2, Hadith 88