Source: Igros Kodesh, vol. 11, no. 3745, section 2.
In the Alter Rebbe's Shulchan Aruch: Orach Chaim, Siman 32, seif 62.
1. Minimum Size Requirements for Tefillin Batim
The discussion today centers on the minimum size required for the tefillin batim—the boxes of the tefillin. While it is well established that the batim must be square, the question arises: is there a minimum size that they must meet? The Shulchan Aruch initially states that any size would suffice for the batim. However, in later generations, specifically from the period of the Go'onim, a standard was instituted requiring that the boxes measure two fingers by two fingers.
2. Which Part of Tefillin Requires This Measurement?
A key point of debate is whether this two-by-two finger measurement refers to the upper part of the tefillin—the box itself—or to the lower part known as the titura. The Rebbe addressed this question, noting that many commentators interpret the requirement as referring to the bottom part. However, in the writings of earlier authorities such as the Pri Megadim, Rashi's opinion is cited to indicate that it refers to the actual batim—the main box. The language used by both the Rosh and the Tur also supports this view, as discussed in Os Chaim. Therefore, those who are meticulous ensure that the main box itself measures two by two fingers.
3. Sources from Chabad Tradition and Halachic Works
The Rebbe further references a letter in which he cites the Alter Rebbe’s Shulchan Aruch. There, it is clear that the requirement of two by two fingers pertains specifically to the top portion of the batim. This reinforces the custom among those who are careful with halachic details to ensure their tefillin meet this standard.
4. Customary Practice and Chassidic Stringency
It has become customary for people to strive for tefillin measuring at least two by two fingers. This practice explains why many Chassidim are seen wearing larger tefillin than average. The intention is to satisfy all opinions regarding these measurements and avoid any doubt about fulfilling this halachic requirement.
5. Height and Proportions of Tefillin Batim
Another aspect discussed is whether there is a required height for tefillin. The Rebbe suggests that ideally, just as length and width should be equal (forming a square), so too should their height match these dimensions, resulting in a perfect cube. This approach ensures that all sides are square and uniform, which aligns with both halachic requirements and Chassidic custom.
6. Variations in Opinion and Practical Considerations
Despite these guidelines, there remain various opinions regarding precise measurements and how strictly they must be followed. This diversity leads some individuals to adopt larger tefillin sizes to accommodate all views and fulfill every possible halachic opinion regarding minimum size requirements for tefillin batim.