The earliest strata of the tradition consistently exempt women from tefillin while leaving open the question of voluntary performance. Mishnah Berakhot 3:3 states plainly that women, slaves, and minors are exempt from Shema and from tefillin, and the Gemara (Berakhot 20b) explains that the exemption requires explicit scriptural derivation lest one reason from the juxtaposition of tefillin to mezuzah — which does bind women — that women should be obligated in tefillin as well.
The scriptural grounding for the exemption is traced in the earliest midrashic sources: the Mekhilta DeRabbi Yishmael (Pischa 17:31) raises the very argument that since both mezuzah and tefillin are positive commandments, women might be thought obligated in tefillin just as they are in mezuzah, then resolves it from the phrase 'that the Torah of God shall be in your mouth' — limiting tefillin to those engaged in Torah study — and concludes that all are obligated in tefillin except women and slaves. The Mekhilta DeRabbi Shimon ben Yochai (13:8) supplies the broader principle: tefillin are a time-bound positive commandment, and women are therefore exempt from all such commandments. The Jerusalem Talmud (Berakhot 2:3) independently derives the exemption from the obligation in Torah study, linking whoever is obligated in Talmud Torah to tefillin and reasoning that since women are not obligated in the former, they are not obligated in the latter — while nonetheless recording that Michal bat Kushi wore tefillin and that the wife of Yonah went on pilgrimage, and that the Sages did not protest either practice.
The Babylonian Talmud engages the case of Michal bat Kushi directly: the Gemara (Eruvin 96a) records that Michal, daughter of Kushi, would don tefillin and the Sages did not protest, and draws from the Sages' silence the inference that they held tefillin to be a positive commandment not bound by time — a view that, if accepted, would mean women could permissibly wear them. Tosafot (Eruvin 96a) builds on this, with Rabbeinu Tam deriving from Michal's practice that women may recite a blessing over time-bound commandments even though they are exempt, since she presumably also recited the blessing without objection from the Sages. Tosafot (Kiddushin 35a) further clarifies the structural logic: tefillin serve as the paradigm case of a time-bound positive commandment from which women are exempt, and the scriptural derivation would have been unnecessary had women been exempt from all positive commandments generally.
The Rishonim codify the exemption while diverging on whether voluntary performance is to be permitted or discouraged. The Rambam (Mishneh Torah, Tefillin 4:13) states concisely that whoever is exempt from Shema is exempt from tefillin. The Sefer HaChinukh (421) rules that the mitzva applies to males but not females as a time-bound commandment, yet adds that if women wish to put on tefillin one does not protest, and that they receive reward — though not the reward of one who is commanded. The Shulchan Arukh (Orach Chayim 39:1) rules separately that tefillin written by a woman are invalid, because the verse 'you shall bind them… you shall write them' is read to mean that only one who is themselves bound by the commandment may write it.
The Shulchan Arukh and later Acharonim close the permissive window that the Sefer HaChinukh left open. The Shulchan Arukh (Orach Chayim 38:3) rules that women and slaves are exempt because tefillin is a time-bound positive commandment, and the Rema adds — citing the Kol Bo — that if women wish to be stringent on themselves, we protest against it. The Levush (Orach Chayim 38:3) explains the reason for protesting: women are not sufficiently careful to maintain the bodily cleanliness that tefillin demand. The Magen Avraham (38) adds nuance, arguing that the concern for bodily purity is not itself the reason for the exemption — since if they were obligated they would be diligent — but it does supply the practical reason to prevent voluntary performance. The Shulchan Arukh HaRav (Orach Chayim 38) combines both rationales, ruling that women are exempt as a time-bound commandment and that if they nonetheless wish to don tefillin we protest because they are not careful to maintain bodily purity.
The Kaf HaChaim (Orach Chayim 38:9–10) adds a further dimension, citing the Targum Yonatan on the verse 'a man's garment shall not be upon a woman' (Devarim 22:5), which he renders as prohibiting the fringes of tzitzit and tefillin — the adornments of a man — on a woman, a view that would make a woman's wearing of tefillin not merely inadvisable but a transgression of a negative prohibition. The Malbim similarly notes this Targum in his commentary (Devarim 22:5), which understood tefillin to be among the items designated exclusively for men.
The Minchas Yitzchak (3:11) concludes, on our reading of the cited page, that while women wearing tefillin during the day carries the appearance of arrogance (yuhra) because they are exempt from the commandment, the particular reading attributed to Rabbeinu Chananel — that Michal bat Shaul wore tefillin specifically at night, when men too are exempt — would not carry that same appearance of arrogance under his analysis.
Igros Moshe (OC 4:11) is not available in full text for Mekoros to read, but our reading of the cited page indicates that the author addresses the halachic validity of a woman tying the knot of tefillin, examining whether tying the knot is legally equated to writing tefillin — which would disqualify women as those exempt from the commandment — or whether the two acts are treated differently by early authorities.
