Yahya said that Malik said, "The situation with us is that one does not have to do wudu for a nose-bleed, or for blood, or for pus issuing from the body. One only has to do wudu for impurities which issue from the genitals or the anus, or for sleep." Yahya related to me from Malik from Nafithat Ibn Umar used to sleep sitting and then would pray without doing wudu.