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The exact order of the four biblical passages (parshiot) within the tefillin shel rosh is critical; if they are not arranged in their specific sequence, the tefillin are disqualified. Abaye and Rava debate the specifics of this requirement, questioning the validity of the tefillin if the two "outer" sections (the first and last) or the two "inner" sections are transposed.

Several physical elements of the tefillin are classified as halakha l'Moshe m'Sinai: the embossed letter Shin on the Shel Rosh, the requirement for the boxes to be perfectly square, the titura (the base), and the ma'abarta (the passageway for the straps).

Regarding the straps (retsuot), the outer side must be black. The underside may be other colors, though red is strictly prohibited. If a strap is partially torn, it is disqualified. The Gemara distinguishes this from tzitzit or a hyssop branch, where "remnants" may still be valid; this is because tefillin straps serve an object of inherent kedusha (sanctity), requiring a higher standard.

The knot of the shel rosh must be shaped like the letter dalet (halakha l'Moshe m'Sinai). Rav Nachman rules that the knot should be prominent and face outward, reflecting the idea that tefillin serve as a sign to the nations that "God's name is called upon you." This purpose also dictates the exact placement of the knot at the base of the skull and the box on the head. Finally, the blessing is recited after the tefillin are placed but before the final wrapping or tightening is completed.

Rav Huna states that a closed-in staircase opening (lul) between a house and an upper story requires one mezuza if it has one entrance and two mezuzot if it has two. Rav Papa infers from this that a room (indrona) with four doors requires four mezuzot, even if the resident typically utilizes only one of them. Amemar rules that a doorway situated at a corner is obligated in a mezuza; though Rav Ashi questions this due to the lack of formal doorposts (patzim), Amemar maintains that the edges of the walls themselves serve as the post.

Rav Papa observes a doorway in Mar Shmuel's house that had only a left-side post yet was fitted with a mezuza. He questions this practice, as it seems to follow Rabbi Meir, who obligates a mezuza for a house with only one post—but even Rabbi Meir only holds that a mezuza is placed on the right side. The source for the right-side placement is derived from the word "beitecha" (your house), which is interpreted as "biatcha" (your entry). The connection between entry and the right side is either because a person begins their entry by leading with the right foot, or it is derived from the verse regarding Jehoiada the kohen, who placed a chest for donations to the right of the altar as people "came in." The dispute between Rabbi Meir and the Rabbis regarding a single doorpost centers on the plural phrasing of "mezuzot." The Rabbis hold this implies a minimum of two posts, while Rabbi Meir explains how the term can signify a single post, based on the interpretations of Rabbi Yishmael and Rabbi Akiva who utilize various exegetical principles.

A braita derives the obligation to write the mezuza on parchment and then affix it to the wall, rather than writing it directly on the stones of the doorpost as might be understood from a simple reading of the verse.

Regarding tefillin, the four paragraphs are all essential (me'akvot); even the omission of a single letter, or the "tip" of the letter yud, renders them invalid. Rav Yehuda in the name of Rav adds that every letter must be surrounded by blank parchment on all four sides. The Gemara discusses the source for the four compartments of the head tefillin (shel rosh). Rabbi Yishmael derives the number four from the number of mentions and spelling variations of the word "totafot," while Rabbi Akiva explains that the word is a compound of "tat" (two in the Katpi language) and "pat" (two in the Afriki language).

A braita clarifies that while the tefillin shel rosh contain four separate scrolls in four compartments, the arm tefillin (shel yad) consist of all four paragraphs written on a single scroll. If one wrote the tefillin shel rosh on one scroll, it is valid, as long as it is put into four separate compartments. If one wrote the tefillin shel yad on four separate scrolls and placed them in one compartment, it is valid, though Rabbi Yehuda requires them to be glued together to appear as one. Rabbi Yosi rules that a tefillin shel rosh can be used on the arm if it is covering by one piece of leather. A contradiction is raised against Rabbi Yosi as Rabbi Yochanan ruled that this is not possible as one cannot lower an item in sanctity, i.e. from the head to the arm.

The order of the paragraphs to be placed in the four compartments of the tefillin shel rosh is established as: kadesh and v'haya ki yeviacha on the right, followed by shema and v'haya im shamoa on the left. To resolve a contradiction with another source that reverses this, Abaye clarifies that each source refers to a different perspective of "right" and "left," depending on whether one is looking from the perspective of the reader or the wearer. Rashi and Rabbeinu Tam (among others) disagree about how to understand the specific order of the tefillin described in the Gemara. Rav concludes that if a scribe switches the order of the paragraphs, the tefillin are invalid.

Rav Yehuda in the name of Shmuel rules that a mezuza written on two sheets or columns is invalid. The Gemara raises a difficulty from a braita that invalidates a mezuza written on two sheets only when it is placed within two separate sippin (doorposts), implying that if it were placed within a single post, it would be valid. The difficulty is resolved by explaining that Shmuel's intent was that even if it is placed in one post, the mere fact that it is "fit" or able to be divided between two posts renders it invalid, as a mezuza.

Regarding the determination of the right side in doorways between two rooms, Shmuel rules that one follows the "heker tzir" (the placement of the hinges). Rav Adda explains that this refers to the socket in which the door hinge turns; the side toward which the door opens is considered the primary room, and the right side is determined according to the direction of entry into that room. Rav Nachman instructed the Exilarch (Resh Galuta), who wished to fix a mezuza in his house before its construction was complete, that he must first hang the doors and only afterward fix the mezuza.

Concerning the manner of placing the mezuza, Rav Yehuda in the name of Rav invalidates a mezuza placed "k'min neger" (like a bolt), meaning like a horizontal bar inserted into the doorway. The Gemara raises a difficulty from the practice in Rabbi's house, where the mezuzot were placed "k'min neger," and resolves it by distinguishing between a completely vertical placement and a horizontal placement. It is further mentioned in this context that Rav Huna would fix a mezuza in the doorway between his house and the Beit Midrash even though Rabbi did not do so, because Rav Huna followed the practice of those accustomed to using that doorway, which renders it a doorway obligated in a mezuza.

In the matter of the mezuza's height, Shmuel rules that it should be placed at the beginning of the upper third of the doorway's height. Rav Huna disagrees, holding that the entire area of the doorway is valid, provided the mezuza is one handbreadth (tefach) away from the ground and one handbreadth away from the ceiling beam. The Gemara raises a difficulty against Shmuel from a braita and resolves it by explaining that Shmuel rules in accordance with Rabbi Yosi, who learns from a hekesh (textual comparison) between "u'kshartam" (tefillin) and "u'khtavtam" (mezuza) that just as tefillin are placed high up, so too the mezuza must be high up in the doorway.

Rava adds that the mezuza should be placed in the handbreadth closest to the public domain so that a person encounters the mitzva immediately upon entry. Rabbi Chanina adds a conceptual dimension: unlike a king of flesh and blood who sits inside while his subjects guard him from the outside, God guards His servants from the outside while they sit inside, as it is written, "The Lord is your guardian."

Additional laws discussed on this page deal with the requirements of a mezuza that depend on the structure of the doorway and the room. Rav Yosef in the name of Rava invalidates a mezuza that was recessed into the thickness of the wall more than a handbreadth. Rava exempts "pitchi shimai" (defective doorways) from mezuza; the Amoraim dispute whether this refers to a doorway without a ceiling or one without a proper doorpost. Similarly, an achsadra (portico) is exempt from mezuza because its posts are intended to support the ceiling rather than to create a doorway.

A gatehouse (beit shaar) that opens both to a house and a courtyard needs a mezeua on both entrances. However, a gatehouse that opens to both a house and a garden, the Tannaim dispute - and the Amoraim dispute the interpretation of their words - whether the obligation is determined by the entry to the house or the exit to the garden. Rav Ashi rules according to the stringency of Rav and Shmuel: any doorway used for entry into a house, even if it leads to an open space like a garden, is obligated in a mezuza.