When determining the kashrus of tefillin the most obvious issue is how often, if ever, should tefillin be opened for the parshios (writing) to be examined. Many are surprised to learn that the Shulchan Aruch (39:10) records that tefillin that are in regular use need not be checked as they have a continued chazaka (assumption) of being kosher. Nevertheless, the Mishna Berura recommends that the parshios be checked as they can potentially be ruined from sweat. The Aruch Hashulchan adds an additional concern that ink today is made differently than in previous generations which warrants concerns about fading. (More on this in a future article). The standard recommendation is that the parshios of high quality tefillin be checked every 15 years.
Beyond the klaf (parchment), there are other issues that affect the kashrus of tefillin which can be seen by just looking at them. The Rambam (Hilchos Tefillin 3:1) records ten aspects of tefillin that were communicated directly by God to Moshe and passed on as an oral tradition (Halacha L’Moshe M’Sinai). While several of those deal with the placement of the parshios and are concealed from view, some of these requirements, which define whether the tefillin are kosher or not, can easily be inspected from the outside.
1. Squareness – There are 3 parts of the tefillin that must be square (Shulchan Aruch OC 32:39). These are the bayis (compartment) itself, the titura (base), and the giddin (threads) used to sew the tefillin shut (picture #1). Many authorities (ex. Igros Moshe YD 3:120:5) recognize that making a precise square is both impossible and unnecessary as halacha only demands that it appear as a square to the naked eye. Nevertheless, with today’s advancements in technology, they should be within 2 mm of a perfect square.
A dented corner of tefillin is one of the most common issues that come up and it is very difficult to give precise parameters of when the tefillin lose their “square” appearance. The Aruch Hashulchan (32:77) points out that while there are experts that can make very precise tefillin, most are not able to do so and “heaven forbid that we should label these as passul.” While the quality and precision of tefillin construction has improved since the time of the Aruch Hashulchan, this rule still holds true. However, we should do our best to treat tefillin with care to ensure they maintain their integrity. If the corners of the tefillin begin to look rounded, it is best to bring to an expert. Repairing tefillin is often not that expensive.
Another issue related to squareness, and specifically of the head tefillin, is the separation of the compartments. While a small separation is not a problem if their square appearance is maintained, small splits can become larger over time. Repairing these defects often require gluing the sections together, which has its own set of issues in halacha.
2. Giddin (threads) – The base of the tefillin is sewn shut with giddin which are made using the sinews of a kosher animal. These giddin can break. While tefillin can still be used if there is one break, a second break could make them passul.
3. Knots – The retzuos (straps) of both the head and arm tefillin have knots that form letters. The knot on the head tefillin forms the letter dalet and the knot on the inside part of the arm tefillin forms the letter yud (picture #2). These two letters, with the addition of the shin that is created on the head tefillin (see picture), form the word Shaddai which is one of the names of God. The Shulchan Aruch (32:52) requires these knots to be intact. While the head tefillin will not stay on one’s head without the knot intact, the knot on the arm tefillin could become undone. A bracha should not be made on tefillin that do not have their proper knots intact (Mishna Berura 32:233).
4. Retzuos (straps) – The two most common issues regarding retzuos are width and color. The opinions for the minimum width of retzuos range from 9mm to 11mm. Standard retzuos sold today are 15 mm wide. However, over the years, the retzuos of the hand tefillin tend to lose some width at the spot where they are tightened. It is important to monitor this to make sure that the retzuos do not become too narrow.
Retzuos must be entirely black on one side. The Beur Halacha (33:3) suggests that even small scratches and specks may invalidate the retzuos. However, many authorities (ex. Halichos Shlomo 4:28) hold that retzuos are acceptable as long as the appearance of black is maintained. Tefillin paint and markers are available for touch ups. When blackening retzuos one should vocalize that he is doing so for the purpose of the mitzva (‘l’sheim mitzvas tefillin).