Regarding the Jewish perspective on Tefillin:
http://www.vbm-torah.org/archive/mb/89mb.htm89. SIMAN 154 - SEIFIM 1-8
SIMAN 154 - WHAT IS CONSIDERED A "TASHMISH KEDUSHA"
In the MB and BH on our siman, we find three distinct levels of sanctification or dedication:
1. KEDUSHA: Sifrei Torah, tefillin, and mezuzuot are considered to have actual "kedusha" - holiness. These are not profane items which were then dedicated to holy use but rather items whose very creation is predicated on an intention to invest them with sanctity.
The MB adds another member of this category in s.k.7. According to the above definition, is this addition still relevant nowadays (for printed books)? The Mishna Berura (s.k.9) seems to imply that it is - but pay attention to the source (from a son of the Rosh, who lived about a hundred years before Gutenberg). We discuss this issue in detail below.
2. TASHMISHEI KEDUSHA - items which serve (mishamesh) objects of kedusha. An example would be a Torah cover.
The MB in s.k.7 adds the pouch in which tefillin are held. Nowadays almost everyone keeps his tefillin in special boxes (the MB calls this a "nartik" - see e.g. MB 42:2.) which cover the whole tefillin. Is the pouch still considered a "tashmish kedusha?" According to s.k.14, it depends on whether we view the pouch as HONORING the tefillin or as PROTECTING them. (For the answer to the question, see Beur Halakha at the end of siman 34 - d.h. "shtei zugot.")
3. TASHMISHEI MITZVA - items which are set aside to be used for a mitzva. In s.k.6 the MB refers us to siman 21; there he mentions the examples of succa, lulav, and shofar. In siman 153 (s.k.37 and 48) the MB implies that a beit knesset also belongs in this category.
The fact that the second level is called a "TASHMISH kedusha" and the third doesn't have the word "kedusha" in its description at all does not mean that levels two and three do not have "kedusha." Of course they do, and the MB refers several times to "kedushat beit knesset." (Example in our siman: BH d.h. "aval aron.") Here are some of the differences.
1. DIVREI KEDUSHA can certainly never be used for any other purpose. Their sanctity can never be conditional. Even preparing something (hazmana) for kedusha may sanctify it. (SA Orach Chaim 42:3.)
2. TASHMISHEI KEDUSHA even if sold in a permissible way retain their sanctity. (MB 153:37.) However, their sanctity CAN be originally conferred temporarily or conditionally. (Rema on Orach Chaim 42:3). The Beur Halakha in our siman (d.h. tashmishei kedusha) discusses if it is ever possible for their sanctity to lapse barring an explicit condition.
3. TASHMISHEI MITZVA if sold in a permissible way lose all of their sanctity - though under some conditions the proceeds may retain it. (MB 153:37.)
In many places the MB refers to a fourth category "tashmish detashmish" - something which serves a "tashmish kedusha." These have NO sanctity (MB 42:9) and the MB on our siman (s.k.6) indicates that at any time they may be diverted to secular purposes.