The foundational source for the obligation is the Sotah ritual, where the Gemara (Ketubot 72a) derives from the pasuk "ופרע את ראש האשה" — and the school of Rabbi Yishmael's teaching that this constitutes a warning to the daughters of Israel not to go out with uncovered heads — that the prohibition at the Torah level applies to a married woman going out in public with her hair entirely uncovered, while Bamidbar Rabbah (9:33) draws from the episode of Tamar a further indication that Jewish women are to cover their heads.
The Gemara then distinguishes two tiers of obligation: Ketubot (72b) rules that covering one's head with a basket (kilta) suffices to avoid a Torah-level violation, but that rabbinic law — "dat Yehudit" — requires a more substantial covering, and locates the operative context as the transition from one courtyard to another through a side-alley, with the courtyard itself being treated more leniently.
Building on that Talmudic framework, the Shulchan Arukh (Even HaEzer 115:4) codifies that going out to a public thoroughfare or a courtyard frequented by many people with one's head uncovered and without a shawl — even if the hair is covered with a kerchief — constitutes a violation of dat Yehudit, the standard of Jewish modesty practiced by the daughters of Israel.
The Acharonim debate the two tiers more precisely: the Beit Shmuel (115:9) formulates the rule that fully uncovered hair in a public domain is a violation of dat Moshe (Torah law), while hair that is covered but not in the manner customary for women constitutes a violation of dat Yehudit, and the Chelkat Mechokek (115:9) adds that uncovered hair even in the passage between courtyards carries the prohibition of priyat rosh, whereas within one's own courtyard it does not render a woman an ovedet dat Yehudit — though he notes debate among earlier authorities about whether it is forbidden outright even there.
On the question of whether the obligation applies inside the home, Peninei Halakhah (Family 7:19) records a dispute between the Tosafot (who hold the obligation applies only when leaving one's house and courtyard) and the Rambam (from whom indoor coverage is implied), and notes that the Chatam Sofer ruled that since the widespread custom of women is to cover their heads even in their private rooms, this has the force of full law — a position endorsed by the Mishnah Berurah — while other authorities are lenient and permit going uncovered at home provided only household members are present.
Peninei Halakhah (Family 7:15) summarizes the majority view of the poskim: at the Torah level it suffices for the hair to be gathered within a net or small cap, while the Sages added that all the hair must be covered with a non-transparent head-covering; crucially, this ruling is not contingent on local custom — even in a place where all women go bareheaded, the practice does not alter the law — and the obligation falls on a married woman but not on an unmarried one.
The Mishnah Berurah (75:10–15) reinforces that even where women in a given locale are accustomed to going bareheaded in public, this does not constitute a valid local practice that removes the prohibition, since the Torah-level requirement applies to all communities of Israel who have maintained this standard throughout the generations, and it is therefore categorized as ervah — a forbidden exposure that disqualifies recitation of sacred texts in its presence.
Shulchan Arukh HaRav (Orach Chayim 75) classifies the hair of a woman who customarily covers it as ervah on account of the improper thoughts it occasions, such that it is forbidden to recite prayers or sacred texts facing it — even if the woman is one's wife — but notes that a sheitel (peah nochrit) does not carry this prohibition even if a woman ordinarily covers her hair, and may be uncovered without triggering the violation of "yatz'ah v'rosah paru'a."
Darchei Tahara (25:19) notes that in places where women wear a sheitel, some hold that a sheitel does not count as a head-covering for purposes of reciting sacred texts opposite it, and that where sheitels are not normally worn it is preferable to be stringent and treat them as one would a woman's own hair — particularly given that contemporary sheitels appear identical to natural hair.
B'Mareh HaBazak (Vol. VI, 12) records a dispute among the poskim regarding whether a married woman is obligated to cover her head specifically during prayer: many rule that she is, while others hold this is merely a custom rather than a strict legal requirement, and that at minimum it is proper for her to cover her head when reciting blessings even if she is not strictly obligated to do so by the core law.
The Magen Avraham (75) addresses the scope of the obligation across marital statuses, noting that Even HaEzer 21:1 and the Rambam (Hilchot Ishut 21) state that no daughters of Israel — whether married or unmarried — should go with uncovered heads in the marketplace, and he resolves this by explaining that the prohibition against unbraided or loosened hair in public applies even to an unmarried woman, while the Torah-level prohibition of fully uncovered hair is limited to married women.
Igros Moshe (OC 1:1) is not available in text for Mekoros to read, but our research indicates that he addresses whether covering only part of a married woman's head fulfills the hair-covering obligation in this source.
Igros Moshe (EH 1:58) is not available in text for Mekoros to read, but our research indicates that he addresses the parameters of head-covering obligations in different contexts and the relationship between local custom and the requirement in this source.
Igros Moshe (EH 1:57) is not available in text for Mekoros to read, but our research indicates that he addresses the distinction between Torah-level prohibition and rabbinic obligation in the context of how much of a married woman's head must be covered in this source.
Nitei Gavriel (Nisuin vol. 2, perek 58) is not available in text for Mekoros to read, but our research indicates that he addresses customs regarding head-covering for a married woman, including the requirement that the covering be opaque and communal variations in when the bride begins covering her head in this source.
Modern poskim have addressed this question directly. Our research indicates that Iggerot Moshe (Even HaEzer 1:58), Tzitz Eliezer (7:48), Ma'ayan Omer (12:2:23), Divrei Yatziv (EH 80), and B'tzel HaChochma (ח"ד סי' קכ"ז) are relevant.
