OPINIONS: The Mishnah (95a) teaches that if one finds Tefilin on Shabbos outside of the settled area, he should wear them in the normal manner in order to bring them to safety in the city (a Reshus ha'Yachid). The Mishnah adds that this law applies only to "Yeshanos" (old Tefilin) and not to "Chadashos" (new Tefilin). The Gemara suggests two ways of understanding the difference between old and new Tefilin.

In the first approach (96b), Rava says that the Mishnah refers to Tefilin whose straps are not tied into the knots of Tefilin. "Chadashos" refers to Tefilin whose straps bear no sign that they were ever tied into knots. "Yeshanos" refers to Tefilin whose straps appear to have been previously knotted and have now become untied. When there are no signs of a knot, one may assume that the object is just a Kamei'a, as a person occasionally troubles himself to make a Kamei'a in the form of Tefilin. When the straps have been previously knotted, one may assume that they are Tefilin. No one would bother to make a Kamei'a that looks like Tefilin and go to the trouble to tie it with the knot of Tefilin (TOSFOS DH v'Chi).

The Gemara (97a) cites a second approach in the name of Avuha d'Shmuel. He explains that "old" Tefilin refers to Tefilin whose straps have already been tied into knots. One merely needs to don them and wear them home in order to bring them to safety on Shabbos. "New" Tefilin refers to Tefilin whose straps have not been tied. One may not bring them home because one is not allowed to make knots on Shabbos. Furthermore, one may not don them without the knots, because this is not considered "wearing" Tefilin but "carrying" them. Therefore, one who finds Tefilin "Chadashos" must leave them in their place until after Shabbos.

Does the Halachah follow the approach of Rava or the approach of Avuha d'Shmuel?

(a) The straightforward reading of the Gemara implies that the Halachah follows the approach of Avuha d'Shmuel. The Gemara appears to reject Rava's suggestion in favor of Avuha d'Shmuel's ("v'Hashta d'Tani..."). Accordingly, one who finds Tefilin without their knots must leave them behind, because one may not tie the knots on Shabbos in order to wear the Tefilin. This is the ruling of TOSFOS (DH Abaye Amar), the BA'AL HA'ME'OR, and the RA'AVAD (Hilchos Shabbos 19:24, Hilchos Tzitzis 2:7). Furthermore, the Halachah is that we do not assume that a person would bother to make a Kamei'a in the form of Tefilin (or make strings that look like Tzitzis).

(b) The RIF, ROSH, and RAMBAM (Hilchos Shabbos 19:24, Hilchos Tzitzis 2:7) rule that one who finds knotted Tefilin may wear them home. However, if one finds Tefilin whose straps are not knotted, he must leave the Tefilin where they are because they are assumed to be a Kamei'a.

The ruling of these Rishonim is difficult to understand. They apparently mix together the Gemara's two explanations. On one hand, they rule like the explanation of Avuha d'Shmuel, who differentiates between Tefilin whose straps are knotted and Tefilin whose straps are not knotted. On the other hand, they also write that when the straps are not knotted, we assume that it is a Kamei'a and not Tefilin. This is not the reasoning of Avuha d'Shmuel, who says that one may not wear Tefilin that are not knotted on Shabbos because he is not allowed to tie their knots.

The Rambam's ruling with regard to one who finds blue strings is similar to his opinion about one who finds Tefilin on Shabbos. The Rambam rules that when one finds short strings dyed with Techeles, he may not use them for Tzitzis, because there is a concern that perhaps they were not dyed for the sake of Tzitzis. We are concerned that a person will go to the trouble to make strings for his garment which look like Tzitzis.

When the Rambam was confronted by the Chachmei Lunil about his ruling with regard to Tzitzis (TESHUVOS HA'RAMBAM #287), he responded that he apologizes for the mistake and that he already corrected his own manuscript with regard to this ruling. He concedes that the Halachah is that a person would not bother to make strings like Tzitzis (or a Kamei'a like Tefilin).

However, the VILNA GA'ON (in BI'UR HA'GRA OC 301:42) points out that the Rambam's ruling with regard to Tzitzis is valid. In fact, his ruling follows that of the Rif (the "Rebbi" of the Rambam and the source for most of the Rambam's rulings; see Introduction of the Rambam to the Mishnah). This is evident from the Rambam's ruling in Hilchos Shabbos, where he writes explicitly that a person does go to the trouble to make a Kamei'a like Tefilin (as the Rif rules). How did the Rif and Rambam understand the Gemara here?

1. The RAMBAN (in Milchamos) explains that Rava does not argue with Avuha d'Shmuel when he says that there is a concern that a person may make a Kamei'a that looks like Tefilin. Rather, Rava understands Avuha d'Shmuel's reasoning differently. When Avuha d'Shmuel says that one may not wear Tefilin that lack knots in order to bring them to safety on Shabbos, he was concerned that perhaps the Tefilin are a Kamei'a. He did not prohibit one to wear them simply because it is forbidden to make a knot on Shabbos. (Even though Abaye says that, according to Avuha d'Shmuel, one may not take the Tefilin home when they are not tied because one may not tie a knot on Shabbos, Rava understands Avuha d'Shmuel's reasoning differently. When Rava and Abaye argue, the Halachah follows Rava.)

2. The VILNA GA'ON (ibid.) explains that the Rif derived his ruling from the Mishnah. Although Rebbi Yehudah maintains that one may not don Tefilin that are not tied because of the prohibition of tying on Shabbos, that cannot be the reason why the Mishnah prohibits it. The Mishnah says that one is "Patur" -- exempt -- from taking the Tefilin to safety. If the Tefilin are genuine and holy Tefilin, then one should at least be obligated to stay with the Tefilin and guard them until Shabbos departs. Why does the Mishnah say that he is "Patur" (a phrase that implies that he is exempt from any obligation with regard to the Tefilin)? The Rif understood, therefore, that he may not take the Tefilin because it is assumed that they are really a Kamei'a, and not Tefilin, as Rava says.

Abaye, however, focuses on Rebbi Yehudah in the Beraisa. The Beraisa says that Rebbi Yehudah is "Oser ba'Chadashos" -- he forbids one to take Tefilin Chadashos to safety. He forbids it, because one is not permitted to tie the knots. The Mishnah and Beraisa express two different reasons which reflect two separate Halachos.