(12) The one who fatally strikes a man shall be put to death.
(22) When men fight, and one of them pushes a pregnant woman and a miscarriage results, but there is no other damage (ason), the responsible person shall be fined -according to the woman’s husband, the payment to be based on judgment. (23) But if other damage ensues, the penalty shall be life for life, (24) eye for eye, tooth for tooth, hand for hand, foot for foot, (25) burn for burn, wound for wound, bruise for bruise.
Regarding the verse: “If men struggle and they hurt a pregnant woman…and if there shall be a tragedy (ason) you shall give a life for a life” (Exodus 21:22–23), It is taught by Rabbi that the reference is to a monetary payment for the life. (The tragedy referenced is the unintentional killing of the mother.)
(א) הַנּוֹגֵף אֶת הָאִשָּׁה וְיָצְאוּ יְלָדֶיהָ אַף עַל פִּי שֶׁלֹּא נִתְכַּוֵּן חַיָּב לְשַׁלֵּם דְּמֵי וְלָדוֹת לַבַּעַל וְנֵזֶק וְצַעַר לָאִשָּׁה:
(1) One who strikes a woman and causes her to miscarry, even though this wasn't his intent, he must pay the value of the fetus to the [woman's] husband, and damage and pain to the woman.
(ו) הָאִשָּׁה שֶׁהִיא מַקְשָׁה לֵילֵד, מְחַתְּכִין אֶת הַוָּלָד בְּמֵעֶיהָ וּמוֹצִיאִין אוֹתוֹ אֵבָרִים אֵבָרִים, מִפְּנֵי שֶׁחַיֶּיהָ קוֹדְמִין לְחַיָּיו. יָצָא רֻבּוֹ, אֵין נוֹגְעִין בּוֹ, שֶׁאֵין דּוֹחִין נֶפֶשׁ מִפְּנֵי נָפֶשׁ:
(6) If a woman is having trouble giving birth, they cut up the child in her womb and brings it forth limb by limb, because her life comes before the life of [the child]. But if the greater part has come out, one may not touch it, for one may not set aside one person's life for that of another.
יצא ראשו - באשה המקשה לילד ומסוכנת וקתני רישא החיה פושטת ידה וחותכתו ומוציאתו לאברים דכל זמן שלא יצא לאויר העולם לאו נפש הוא וניתן להורגו ולהציל את אמו אבל יצא ראשו אין נוגעים בו להורגו דהוה ליה כילוד ואין דוחין נפש מפני נפש ואם תאמר מעשה דשבע בן בכרי (שמואל ב כ׳:כ״א) הנה ראשו מושלך אליך דדחו נפש מפני נפש
its head came out: With a women that is experiencing difficulty giving birth and is in [mortal] danger. And it is taught in the first section [of this teaching], "the midwife extends her hand and cuts it up and extracts [the pieces];" as the entire time that that it has not gone out into the air of the world, it is not [considered] a soul, and [so] it is possible to kill it and to save its mother. But when its head came out, we cannot touch it to kill it, as it is like a born [child]; and we do not push off one soul for the sake of another.
(ב) מכה איש .. שומע אני אף בן שמונה במשמע – תלמוד לומר מכה איש מגיד שאינו חייב עד שיהרוג בן קיימא.
"And if a person strikes any soul (nefesh) of a person, and he dies, he shall be put to death.” (Leviticus 24:17): I might think that an eight-month birth, (who is destined to die,) is also included. It is, therefore, written "If one strikes a man" — whereby we are apprised that he is not liable unless he kills one who is destined to live.
(ז) הַמַּפֶּלֶת לְיוֹם אַרְבָּעִים, אֵינָהּ חוֹשֶׁשֶׁת לְוָלָד. לְיוֹם אַרְבָּעִים וְאֶחָד, תֵּשֵׁב לְזָכָר וְלִנְקֵבָה וּלְנִדָּה. רַבִּי יִשְׁמָעֵאל אוֹמֵר, יוֹם אַרְבָּעִים וְאֶחָד, תֵּשֵׁב לְזָכָר וּלְנִדָּה. יוֹם שְׁמוֹנִים וְאֶחָד, תֵּשֵׁב לְזָכָר וְלִנְקֵבָה וּלְנִדָּה, שֶׁהַזָּכָר נִגְמָר לְאַרְבָּעִים וְאֶחָד, וְהַנְּקֵבָה לִשְׁמוֹנִים וְאֶחָד. וַחֲכָמִים אוֹמְרִים, אֶחָד בְּרִיַּת הַזָּכָר וְאֶחָד בְּרִיַּת הַנְּקֵבָה, זֶה וָזֶה לְאַרְבָּעִים וְאֶחָד:
(7) If a woman miscarried on the fortieth day, she need not be concerned that it was a valid childbirth...The sages say: the fashioning of the male and the fashioning of the female both take forty-one days.
...And if she is pregnant, until forty days from conception the fetus is merely water. It is not yet considered a living being...
...Rabbi Yehuda haNasi holds: A fetus is considered as its mother’s thigh...
(ט) אַף זוֹ מִצְוַת לֹא תַּעֲשֶׂה שֶׁלֹּא לָחוּס עַל נֶפֶשׁ הָרוֹדֵף. לְפִיכָךְ הוֹרוּ חֲכָמִים שֶׁהָעֻבָּרָה שֶׁהִיא מַקְשָׁה לֵילֵד מֻתָּר לַחְתֹּךְ הָעֵבָּר בְּמֵעֶיהָ בֵּין בְּסַם בֵּין בְּיָד מִפְּנֵי שֶׁהוּא כְּרוֹדֵף אַחֲרֶיהָ לְהָרְגָהּ. וְאִם מִשֶּׁהוֹצִיא רֹאשׁוֹ אֵין נוֹגְעִין בּוֹ שֶׁאֵין דּוֹחִין נֶפֶשׁ מִפְּנֵי נֶפֶשׁ וְזֶהוּ טִבְעוֹ שֶׁל עוֹלָם:
(9) This, indeed, is one of the negative mitzvot - not to take pity on the life of a rodef (pursuer). On this basis, our Sages ruled that when complications arise and a pregnant woman cannot give birth, it is permitted to abort the fetus in her womb, whether with a knife or with drugs. For the fetus is considered a rodef (pursuer) of its mother. If the head of the fetus emerges, it should not be touched, because one life should not be sacrificed for another. Although the mother may die, this is the nature of the world.