Gemara

(Rav Hamnuna): Eglah Arufah becomes forbidden when it is alive.

(Rava): It becomes forbidden after Arifah.

Sanhedrin 47b (Abaye): If one wove a garment for a Mes, one may not benefit from it;

(Rava): One may benefit from it.

Abaye forbids, because Hazmanah (preparation) takes effect. Rava permits, for Hazmanah has no effect.

(Rav Chisda): If a cloth was designated and used to wrap Tefilin, one may not wrap coins in it. If it was designated but not yet used to wrap Tefilin, or used but not designated, one may wrap coins in it.

Abaye holds that it depends only on Hazmanah. If it was designated, even if it was not yet used for Tefilin, one may not wrap coins in it. If it was not designated, even if it was used for Tefilin, one may wrap coins in it.

48b - Question (against Rava): If a bag was made to hold Tefilin, one may not put coins in it. If it was not made for Tefilin but Tefilin were put in it, one may put coins in it.

Answer: The Reisha should say 'if it was made for Tefilin and Tefilin were put in, one may not put coins in it (like Rav Chisda taught above).

Question (against Abaye - Beraisa): If Reuven told a craftsman 'make me a cover for a Sefer Torah (or for Tefilin)', he may use it for Chulin only until he uses it for Kodesh. Afterwards, it is forbidden.

Answer: Tana'im argue about Hazmanah.

(Beraisa): Hide of a Tahor animal is Kosher for Tefilin boxes, even if the hide was not tanned for Tefilin;

R. Shimon ben Gamliel says, if the hide was not tanned Lishmah (for the sake of Tefilin), it is Pasul.

The Halachah follows Rava.

Menachos 42b (Rav): Even Tzitzis made from Sisin are Kosher (even though they were not spun Lishmah);

(Shmuel): They are Pasul. Tzitzis must be spun Lishmah.

Rav and Shmuel argue like the Tana'im (in the Beraisa above).

Question (Abaye): How do you dye Techeles strings?

Answer (Rav Shmuel bar Rav Yehudah): We take the blood of the Chilazon and cook it. To see if it finished cooking, we dye a tuft of wool in it. We burn the tuft.

Inference: The dying must be Lishmah. (We burn the tuft, for it was not dyed l'Shem Mitzvah.)

Gitin 54b: A scribe said 'the Sefer Torah that I wrote and gave to Ploni, I did not tan the hide for the parchments Lishmah.'

R. Avahu: Since you are believed to forfeit your wages, you are also believed to disqualify the Sefer Torah.

Rishonim

Nimukei Yosef (Sanhedrin 15a DH Sudrei): He wrote that here we discuss Hazmanah of Tashmishim (what serves the matter), but Hazmanah of the matter itself helps, e.g. tanning hide for Tefilin boxes or parchments. If one did so Lishmah, this Hazmanah alone forbids using them for Chulin. We require tanning Lishmah for Seforim, Tefilin and Mezuzos, but not for the straps, for they are Meshamshim. Hazmanah of Meshamshim is not significant. Menachos 42b connotes like this.

(Note: I suspect that 'he' refers to the Ritva, whom the Nimukei Yosef often cites, who often says mi'Pi Mori ha'Rav Nero'.)

Tosfos (Menachos 42b DH Ad): R. Tam says that the Halachah follows R. Shimon ben Gamliel. Even though the Halachah follows Rav in Isurim, the Sugya in Gitin is like R. Shimon ben Gamliel. Abaye and Rava argue about whether Hazmanah is significant. The Gemara says that they argue like the Tana'im who argue about Lishmah. Rashi says that Rava holds like Rabanan, who do not require tanning Lishmah, for Hazmanah is not significant. R. Tam explains that Rava holds like R. Shimon ben Gamliel. Since he requires tanning Lishmah, Hazmanah is not significant. If Hazmanah were significant, it would suffice to cut the hide and do minor preparations to make them Lishmah. Abaye asked Rav Shmuel about dying Techeiles, and he answered like R. Shimon ben Gamliel (it must be dyed Lishmah). Abaye did not accept the answer. Some say that the Sugya in Gitin is even like Rabanan. They argue about only about the leather (for the boxes), which are Meshamshim of a Mitzvah. This is wrong. The Shin (on the box of the head) is Ikar Kedushah. This is clear from Shabbos 28b. (We require skin of a Tahor animal for the boxes, just like for the parchments, due to the Shin on the box of the head Tefilin.)

Ba'al ha'Ma'or (Sukah 4b): The Ge'onim wrote unlike Rashi. Here, Rabanan said that the Halachah follows Shmuel. Since he holds like R. Shimon ben Gamliel, the Halachah follows R. Shimon ben Gamliel. Abaye and Rava argue about shrouds, like Rabanan and R. Shimon ben Gamliel. Weaving for a Mes is Hazmanah. It is unlike tanning for straps. There is a Mitzvah to tie straps. There is no Mitzvah with shrouds, just they are forbidden with the Mes when they are put on it. Whatever came before is Hazmanah; it does not forbid them. Likewise, one may change Tefilin straps after tanning before attaching them to the boxes. Hazmanah does not forbid them. We rule like Rava, that Hazmanah is not significant. This is like Tosfos, unlike Rashi. Rava holds Hazmanah is not significant regarding Gufo Kedushah (Kedushah itself), for he learns Meshamshim from Meshamshim, and not from Eglah Arufah, which is Gufo Kedushah.

Rebuttal (Milchamos Hash-m): Margins of Kisvei ha'Kodesh are Kodesh along with the writing. If the writing fades, also the Kedushah of the margins goes away (Shabbos 116a). Therefore, it is unlike Eglah Arufah, which is Gufo Kedushah. Even though (the straps) require tanning Lishmah, one may change them, for Hazmanah is not significant.

Poskim

Rema (OC 42:3): If a parchment was tanned for the sake of Tefilin, one may not write Chulin on it, for such Hazmanah for Guf ha'Kedushah is significant.

Magen Avraham (6): The Nimukei Yosef says that the parchment and boxes are considered the Kedushah itself. However, the straps need not be tanned Lishmah. They are Meshamshim. Hazmanah is not significant for them. The Gemara in Menachos connotes like this. It seems that the Nimukei Yosef holds like Rashi, that the one who holds that Hazmanah is not significant does not require tanning Lishmah. Gufo Kedushah require tanning Lishmah, therefore Hazmanah is significant. This does not apply to the straps. From 32:37 and 33:3, we see that we hold like Tosfos. In Hilchos Tefilin 7a (DH she'Lo and DH R. Shimon), the Nimukei Yosef himself rules like Tosfos! This requires investigation. The Ramban (Milchamos Hash-m) concluded that even though the straps require tanning Lishmah, one may change them, for Hazmanah is not significant. Tosfos (Sanhedrin 47b DH Mai) says that Rava rules like R. Yochanan, that Eglah Arufah is not forbidden until Arifah. If so, all the more so regarding Tefilin (the straps are not Kodesh until the Tefilin are written).

Gra (DH Klaf): The Rema is like Tosfos in Menachos. Even though Hazmanah is not significant, tanning Lishmah suffices (to forbid). See the Nimukei Yosef. This is unlike the Magen Avraham. Therefore, the Nimukei Yosef wrote 'but not for the straps (Hazmanah of Meshamshim is not significant). Why is tanning Lishmah for straps different than weaving a garment for shrouds? Rather, the Ba'al ha'Ma'or answered that a garment for shrouds is Meshamshim. Tanning is different. However, the Ba'al ha'Ma'or wrote that the straps are primary Kedushah. There is a Mitzvah to tie straps. The Ritva (Gitin 45b DH Tzipan) answered that Rabanan argue with R. Shimon ben Gamliel not due to Hazmanah, for surely hmzn for Gufo Kedushah is significant. Rather, he does not require Lishmah even for writing Tefilin. They are more lenient than Sefer Torah and Mezuzah, just like Tefilin are more lenient and do not require Sirtut (scratching a line to ensure that he writes straight). R. Shimon ben Gamliel argues even about Meshamshim, like Abaye. The Beraisa 'make for me a cover for a Sefer Torah', is like Rava, that Hazmanah for Meshamshim is not significant. A Sefer surely requires Lishmah! We hold like R. Shimon ben Gamliel and Shmuel, who require Lishmah for Gufo Kedushah. For Meshamshim, we do not require Lishmah and Hazmanah is not significant, unlike R. Shimon ben Gamliel and Abaye. This requires investigation, for R. Shimon ben Gamliel mentioned only Gufo Kedushah, and Rava admits about this. Why does the Gemara say that they argue like Tana'im? All hold like Rava! The Tana'im argue about Lishmah! Tosfos holds that Hazmanah is not significant even for Gufo Kedushah.

Mishnah Berurah (18): We discuss leather tanned for the parchments or the boxes, even for the hand Tefilin. Even though there is no letter (of Hash-m's name of the hand box), it is called Gufo Kedushah, and all the more so leather tanned for a Sefer Torah or Mezuzah.

Mishnah Berurah (19): However, one may use it for a lower Kedushah, e.g. for a Mezuzah which has less Kedushah than Tefilin, or other Divrei Torah, even on parchment tanned for a Sefer Torah. One may not write a Get, for it is Chulin, unless one stipulated from the beginning.

Mishnah Berurah (20): Only a proper action forbids them, but not mere verbal designation or mere preparation of the parchment or Sirtut Lishmah.

Mishnah Berurah (21): One should be stringent about leather tanned for straps, if it is not pressed circumstances.

Mishnah Berurah (22): Hazmanah for the Mitzvah itself, e.g. Tzitzis, Shofar Lulav, Sukah, or Ner Chanukah, even if it was made for this, does not forbid, for Hazmanah is not significant. One may use them for Chulin, without a stipulation.

Mishnah Berurah (23): In Sa'if 1 we permit to lower the Kedushah of head Tefilin to hand Tefilin (before one used them), for Hazmanah is not significant. Even though that is Gufo Kedushah, there is different, for one will still use them for some Kedushah. Hazmanah in Gufo Kedushah forbids using them for Chulin. The Magen Avraham brings opinions that even for Gufo Kedushah, Hazmanah is not significant. In practice, one should be stringent like the first opinion. A stipulation helps. If one already began writing Tefilin or Mezuzah or Kisvei ha'Kodesh on the parchment, one may not write Chulin afterwards, for this was an act of Kedushah itself. A Tanai does not help for this.