Abu Qasim [Al-Khiraqi] said: That which annuls a state of purity [tahara] is what comes out of one’s front part or rear part.
Everything that comes out from the two passages [al-sabilain; i.e. the front and the rear] can be summed up into two categories: first, what is commonplace, such as urine, feces, semen, pre-ejaculate, prostatic secretion, and gas; all of these invalidate one’s ablution. Ibn Al-Mundhir said: Scholars are in unanimous agreement that feces coming out of one’s rear, urine coming out of a man’s penis or a woman’s front part, pre-ejaculate coming out, and gas coming out of one’s rear, are all bodily occurrences [hadath]; each of these annuls a state of purity and makes ablution necessary. Moreover blood from vaginal bleeding annuls a state of purity according to the general opinion of scholars, except that of Rabi’a. The second category are things that are uncommon, such as blood, worms, stones, and hair; these also invalidate ablution.