Women, slaves and children are excused from reciting the Shema and from Tefillin, but they are required [to recite] the Amidah and [to affix] a Mezuzzah and [to recite] Birkhat ha-Mazon [Grace after Meals].
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The Amidah is our central act of liturgical worship. Since it is the subject of the next part of our Tractate and in chapters Four and Five will be treated at length, I shall leave all further explanation until then.
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The Hebrew word Mezuzzah quite literally means 'doorpost' – the wooden or metal structure that fits inside the entrance-way to support it on either side and on which the actual door may be hung. However, the applied meaning of the word serves to indicate a small piece of parchment upon which a qualified scribe has written two Hebrew texts: the first two paragraphs of Keri'at Shema, both of which contain the mitzvah of Mezuzzah [Deuteronomy 6:9 and 11:20]. This piece of parchment is rolled up lengthwise from left to right and is enclosed in a container (to protect the contents from the ravages of weather and atmosphere). This container is affixed to the doorpost. (It is, of course, the parchment and not its plastic or wooden container that is the holy Mezuzzah.) Just as the Tefillin serve as a physical reminder of God's sovereignty and as a statement of our personal loyalty to that premise, so the Mezuzzah serves identical purposes. It also serves as a reminder that the attribute of absolute sovereignty contains within it the assurance of protection (ancient monarchs had the moral duty to protect their loyal subjects).
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Ideally, a Mezuzzah should be fixed to every entrance-way – not just to the main entrance and not just to those entrances within the building that have doors in them. Any hole in a wall that serves as an entrance and that has the halakhic shape of an entrance (a lintel and two doorposts adjacent to it at right-angles) [tsurat ha-petaĥ] requires a Mezuzzah to be affixed within the upper third of the right-hand doorpost. Our sources record a difference between Rashi and his almost equally famous grandson as to how the Mezuzzah is to be fixed to the doorpost: of of these sages was of the opinion that it should be fixed upright while the other felt that it should be fixed horizontally. Since then custom, not wishing to decide between two halakhic giants, has advocated compromise, and the Mezuzzah is fixed at an angle of 45 degrees! It is forbidden for an observant Jew to reside in an abode that does not have a Mezuzzah. In the Diaspora since all abodes are considered to be temporary (!) we are given 30 days' grace to perform the mitzvah; that period of grace does not apply in Eretz-Israel. When affixing a Mezuzzah a berakhah must be made: "… Asher Kiddeshanu be-mitzvotav ve-tzivvanu likbo'a Mezuzzah" ["… Whose mitzvot hallow us, one of which is the mitzvah to affix a Mezuzzah"]. (When affixing several Mezuzzot in one session – in a new home for instance – one berakhah is sufficient.) Mezuzzot should be dismantled for competent examination every couple of decades: as already noted, the elements can wreak havoc with the script, and an imperfect Mezuzzah is no Mezuzzah at all. As our mishnah clearly states, all Jewish adults are equally required to observe this mitzvah.
The above notes are intended to be descriptive and not prescriptive. For practical guidance please consult your local Rabbi. I am sure that he or she will be delighted to advise you. Failing that, you can always contact me via private e-mail.
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Birkat ha-Mazon [Grace after Meals] is a subject dealt with at length later on in our Tractate, so I shall leave all further explanation until then.