Menachos Daf 42 מנחוס דַף 42

Rav Nachman once saw Rav Adda bar Ahavah putting tzitzis onto his garment, and making a berachah "לעשות ציצית" – to make tzitzis. Rav Nachman said: מאי ציצי שמענא – “What is this “tzizi” sound I hear? Rav said attaching tzitzis does not require a berachah!” Rav Chisda posed a contradiction in Rav’s ruling, because Rav said that tzitzis made by an עכו"ם are פסול. Rav Yosef explained that Rav Chisda holds that one recites a berachah for a mitzvah which is invalid when performed by an עכו"ם, but not for a mitzvah which an עכו"ם can perform. However, this assertion is refuted from the laws of tefillin, because tefillin written by an עכו"ם are פסול, yet one does not recite a berachah upon making them!? Therefore, the Gemara concludes: כל מצוה דעשייתה גמר מצוה – any mitzvah whose performance is the completion of the mitzvah, such as מילה, one recites a berachah over it even if an עכו"ם can perform it, and any mitzvah which is not completed by its performance, such as writing tefillin, one does not recite a berachah even if it is invalid when done by an עכו"ם. The machlokes about reciting a berachah over attaching tzitzis depends on whether it is a חובת טלית (and is completed then), or a חובת גברא (and completed when worn).

Rav Yehudah said that Rav said: עשאן מן הקוצים – if one made [tzitzis] from thornlike threads (left in the garment from the weaving process), ומן הנימין – or from threads left from sewing the hem, ומן הגרדין – or from fringes hanging from the garment’s edge, it is פסול, because we require עשייה לשמה – [attaching] it for the sake of the mitzvah. If it was made מן הסיסין – from balls of weaving thread, it is כשר, since he attached the tzitzis to the garment for the sake of tzitzis. When Rav Yehudah reported Rav’s ruling to Shmuel, he said that even tzitzis made from balls of thread are פסול, because בעינן טוייה לשמה – we even require spinning of the threads to be for the sake of [tzitzis]. This parallels a machlokes Tannaim: the Tanna Kamma says that although tefillin covered with gold, or the hide of a nonkosher animal, are invalid, they are valid when covered with the hide of a kosher animal, ואף על פי שלא עיבדן לשמן – even though he did not tan them for the sake of [tefillin]. Rabban Shimon ben Gamliel says that even a kosher animal’s hide is פסול unless it was tanned לשמה.

Rav Shmuel bar Yehudah explained how he dyes techeiles: he takes blood of the חלזון with some herbs, then puts them in a pot and boils it up. He then takes a bit of the dye in an eggshell, וטעמינן להו באודרא – and tests it with a wad of wool to check the dye’s quality. The rest of the dye in the eggshell is spilled out, and the wad of wool used for testing is burned. The wad is burned because טעימה פסולה – [wool dyed for] testing is unfit to be used for tzitzis. The reason for this is דבעינן צביעה לשמה – we require dying of תכלת for the sake of [tzitzis]. The dye in the eggshell is spilled out and not returned to the vat because טעימה פסלה – [dye used for] testing invalidates all the dye if it is returned to the vat. Tannaim argue if testing dye disqualifies it: Rebbe Chanina ben Gamliel says that "כליל תכלת" – completely techeiles teaches that dye which was used for testing is disqualified for techeiles, but Rebbe Yochanan ben Dahavai says even the מראה שני – second shade produced by the dye is fit for techeiles, because the passuk says "ושני תולעת" – and a thread of red wool, darshened as a second dyeing.