When the ox performs its gorings at intervals, its owner is liable; if it performs its gorings successively, is it not all the more so that its owner is liable? They said to R' Meir: The halakha with regard to a woman who experiences a discharge of uterine blood after her menstrual period [zava] will prove that your a fortiori inference is invalid: If her sightings occur at intervals, i.e., if she sees a flow of uterine blood on 3 consecutive days, she becomes ritually impure; while if her sightings were consecutive, for example if all 3 occurred on the same day, she remains pure.
אמר להן, הרי הוא אומר: ״וזאת תהיה טמאתו בזובו״ – תלה הכתוב את הזב בראיות, ואת הזבה בימים.
R' Meir said to them: The case of the zava does not disprove my opinion, because the verse states in reference to the parallel halakha of a man who experiences a gonorrhea-like discharge [zav]: “And this should be his ritual impurity when he has a discharge” (Leviticus 15:3). The word “this” emphasizes that in this matter the halakha requires following the instructions of the verse precisely as they were recorded, and in this case the verse associates the impurity of the zav with the number of sightings of discharges the man observed, and it associates the impurity of the zava with the number of days during which she experienced sightings of blood, as it says: “Many days” (Leviticus 15:25). By contrast, with regard to the goring ox, the a fortiori inference remains in place.
ממאי דהאי ״וזאת״ – למעוטי זבה מראיות? אימא למעוטי זב מימים! אמר קרא: ״והזב את זובו לזכר ולנקבה״ – מקיש זכר לנקבה; מה נקבה בימים, אף זכר בימים.
The Talmud asks about this interpretation: From where is it determined that this additional phrase: “And this,” serves to exclude a zava from having her status determined by individual sightings of blood, associating it instead with the number of days on which she experienced bleeding? Say instead that it serves to exclude the zav from having his status determined by sightings on separate days, indicating that he will be rendered a zav only if he experienced 3 discharges on a single day and not on separate days. The Talmud answers: The verse states elsewhere: “And one who has a discharge, whether it be a man or a woman” (Leviticus 15:33). The verse juxtaposes the ritual impurity of a male to that of a female to teach that just as the female’s ritual impurity is caused by sightings on multiple days, so too the ritual impurity of a male can be caused by sightings on multiple days.