Mishnah Zavim 2

¹All persons become unclean through zivah, even converts, even slaves whether freed or not, a deaf-mute, a person of unsound senses, and a minor, a eunuch whether [he had been castrated] by man, or was a eunuch from [the time of seeing] the sun. With regard to a tumtum and an androgynous [person], they place upon him the stringencies for a man and the stringencies for a woman: they defile through blood like a woman, and through eggy [substance] like a man. Their uncleanness still remains in doubt. ²There are seven ways in which a zav is examined as long as he had not become subject to zivah: With regard to food, drink, as [to what] he had carried, whether he had jumped, whether he had been ill, what he had seen, or what he had thought. [It doesn't matter] whether he had thoughts before seeing [a woman], or whether he had seen [a woman] before his thoughts. Rabbi Judah says: even if he had watched beasts, wild animals or birds having intercourse with each other, and even when he had seen a woman's dyed garments. Rabbi Akiva says: even if he had eaten any kind of food, be it good or bad, or had drunk any kind of liquid. They said to him: Then there will be no zavim in the world!’ He replied to them: you are not held responsible for the existence of zavim!’ Once he had become subject to zivah, no further examination takes place. [Zov] resulting from an accident, or that was at all doubtful, or an issue of semen, these are unclean, since there are grounds for the assumption [that it is zivah]. If he had at a first [issue] they examine him; On the second [issue] they examine him, but on the third [issue] they don't examine him. Rabbi Eliezer says: even on the third [issue] they examine him because of the sacrifice. ³One who had [a discharge of] semen does not defile due to zivah for a period of twenty-four hours. Rabbi Yose says: [only] that day. A non-Jew who had a discharge of semen and then converted, he immediately becomes unclean due to zivah. [A woman] who had [an issue] of blood, or had experienced difficulty [in childbirth], [the time prescribed] is twenty-four hours. One who strikes his slave, the "day or two" is twenty-four hours. A dog that eats a corpse's flesh, for three days from one time of day to the same time of day, it is considered to be in its natural state. ⁴A zav defiles the objects that are lain upon (or sat upon) in five ways, so that they defile people and garments: by standing, sitting, lying, hanging or leaning. What he lies upon defiles a person in seven ways, so that he [in turn] defiles garments: by standing, sitting, lying, hanging, or leaning upon it, or by touching or carrying it.