What are the connotations of "mi'Temol Shilshom"?
Rashi: It means that the ox gored three times, 1 and has now become a Mu'ad.
"T'mol" is one, and "Shilshom", two (Sifsei Chachamim).
What is the meaning of "ve'Hu'ad bi'Va'alav"?
Rashi: The Din Mu'ad will only apply if the owner is warned 1 after each of the three initial gorings.
Having already written "u'Meis" (in Pasuk 28), why does the Torah insert the word "v'Hemis"?
Rashi: To teach us that 'goring' is Lav Davka, and that the same Din will apply if the animal kills a person by biting, pushing or kicking 1 him.
Moshav Zekenim: Also these are Toldos of Keren. If the damager benefits, this is Shen; if it normally happens when it walks, this is Regel. There is Kofer for Shen and Regel, but the animal is not killed.
What sort of Misah is the owner of the ox subject to?
Rashi, Ramban (citing the Mechilta), Rashbam, Seforno and Targum Yonasan: He is Chayav Misah bi'Ydei Shamayim. 1
Targum Onkelos: He is Chayav Misah be'Veis-Din. 2
Unless he pays Kofer (Rashbam), provided there are witnesses (Seforno); and we learn this from the words "Rotze'ach Hu" (in the Pasuk "Mos Yumas ha'Makeh, Rotze'ach Hu" [Bamidbar 35:21], in connection with a murderer), implying that a murderer is Chayav through Beis-Din for his own act of murder, but not for an act perpetrated by his ox (Rashi). According to the Ramban, the Lashon "Yumas" implies Shamayim, like we find in Bamidbar (18:7) and in Vayikra (22:9).
Why does the Torah find it necessary to add "Oh Ishah"?
Ramban (citing Kidushin, 35a): To teach us that one is Chayav for killing a woman just like one is Chayav for killing a man. 1
See Torah Temimah (citing Bava Kama, 42b), who explains that the Torah writes it to compare a woman to a man, inasmuch as, just like the Nezek of a man goes to his heirs, so too, does the Nezek of a woman.
Rashi writes that v'Hemis includes other ways that it killed. If so, why does it say (Pasuk 28) "v'Chi Yigach"?
Riva citing R"A: If not for v'Chi Yigach, one might have thought that he is liable only if it killed like other killers, but not through goring.
Bartenura: It needed to teach Negichah, that it is one of the four Avos Nezikim.
Rashi writes that v'Hemis includes other ways that it killed. Why is this needed? They are Toldos (derivatives) of goring (Bava Kama 2b)! And Bava Kama 42b learns from v'Hemis that Nezek owed to a woman goes to her heirs!
Gur Aryeh: We can know from reasoning [that these are Toldos, and one pays for them], but we cannot kill the ox from reasoning; we need a verse.