Gemara

9b: "V'Shilashta" teaches that the Arei Miklat (refuge cities) must be Meshulashim. The following distances were the same: from the south (of Eretz Yisrael) to Chevron, from Chevron to Shechem, from Shechem to Kadesh, and from Kadesh to the north (of Eretz Yisrael).

10a - Question: Why were the extremes (north and south of Eretz Yisrael) further from an Ir Miklat (a quarter of the length of Eretz Yisrael) than the interior (no place was more than half this far from an Ir Miklat)?

Megilah 19a (R. Chelbo): The Megilah is called "Sefer" and it is called "Igeres" (a letter). "Sefer" disqualifies a Megilah sewn with flax (such a Sefer Torah is Pasul). 'Igeres' teaches that if he sewed three stitches of sinews, it is Kosher.

(Rav Nachman): The stitches must be Meshulashim.

19b (R. Chiya bar Aba): We have a tradition from Sinai that one should not entirely sew together the parchments of a Sefer Torah (he should leave some of the top and bottom unsewn).

He retracted (it is not really from Sinai). This is only so it should not tear.

Eruvin 57a (Mishnah - R. Meir): We give a Karfef (an outskirt of about 70 Amos) to a city (before measuring the Techum).

Chachamim say, we give a Karfef only between two cities. If after giving 70 Amos to each city, the areas overlap, the cities are considered like one.

The same applies to three cities that are Meshulashim. If the furthest cities are less than 140 Amos apart, the middle city makes them like one.

(Rav Huna): Two Karfifos are given for two cities.

Question (Mishnah): The same applies to three cities that are Meshulashim. If the furthest ones are less than 140 Amos apart, the middle one makes them like one.

Inference: If not for the middle city, they would not be like one!

Answer: Rabah explained, they are not evenly spaced in a line (rather, they are in a triangle). If we would project the third city between the other two and it would be within 140 Amos of each of them, then all are like one.

(Mishnah): White spots in the cornea are considered a permanent Mum (blemish) if they persist for 80 days.

R. Chanina ben Antigonus says, we check three times within 80 days.

39a (Rav Nachman bar Yitzchak): The three times must be Meshulashim.

Yevamos 80a (R. Yitzchak bar Yosef): A Seris Chamah is one who was a Seris (a male who does not develop like a normal male) from birth.

Since he was and is a Seris at the beginning and the end, we are not concerned lest he was better in the middle.

Question (Rav Mari - Beraisa - R. Chanina ben Antigonus): We check three times within 80 days. (Perhaps it improved in the middle!)

Rishonim

Rif (Megilah 6b). If he made three stitches of sinews in it, it is Kosher. There is one at each end, and one in the interior. Rav Nachman says that they must be Meshulashim.

Rosh (Megilah 2:5): The Rif says that Rav Nachman says that they must be Meshulashim, i.e. the stitch in the interior must be in the middle. Eruvin 57b is like the Rif. If three cities are Meshulashim and the outermost ones are more than 140 Amos apart, and the middle one is exactly in the middle, it makes them like one. In Bechoros, Rav Nachman bar Yitzchak taught that the three times we check the Mum must be Meshulashim, i.e. at the beginning, after 40 days, and at the end of the 80 days. Yevamos proves that this Perush is correct. Rashi explains Meshulashim to mean that there is as much space from the end of the Tefer (stitch; some say that the text of Rashi should say 'Sefer') to the place where the sinew is sewn as from it to the second stitch, and similarly from the second stitch to the third equals from the third to the end. We find such a Perush regarding Arei Miklat. "V'Shilashta" teaches that they must be Meshulashim. The distance from the south to Chevron was the same as from Chevron to Shechem, and from Shechem to Kadesh was like from Kadesh to the north. Because there are two Perushim, one must be stringent about Megilah and fulfill both of them. He must make five stitches with sinews.

Rif and Rosh (7): R. Chiya taught that leaving a remnant is a tradition from Sinai. We conclude that it is only so it will not tear.

Ran (DH DH Shi'ur): Therefore, if there is no remnant, it is Kosher.

Korban Nesanel (6): Therefore, the Rif does not mean that two stitches are at the very end. Also, since it is only so it will not tear, it applies also to Megilah.

Rambam (Hilchos Megilah 2:11): A Megilah must be tied so that all the parchments are one Megilah. It must be sewn only with sinews, like a Sefer Torah. If it was sewn with anything else, it is Pasul. One need not sew the entire parchment with sinews, like a Sefer Torah. Rather, even if he sewed three stitches at one end, three in the middle and three at the other end, it is Kosher, for it is called a letter.

Gra (OC 691:26): the Rambam explains like the Rif, just he requires three threads in each stitch. This is like "Eglah Meshuleshes v'Ez Meshuleshes" (Bereishis 15:9). See the Targum (three calves and three goats).

Tosfos (Bechoros 39a DH she'Yehu): Here, Meshulashim means at the beginning, end and middle. We can explain similarly in Megilah. Rashi explained there that the spaces between the outermost stitches to the end equal the spaces between the stitches themselves. This is like the Arei Miklat. We do not say that they were at the ends and middle of Eretz Yisrael. Here, Rashi explained that we check after 26, 53 and 80 days. He tried to make it like in Makos. He could not say exactly like there, that we check after 20, 40 and 60 days (for if so, the test is not for 80 days)! However, Yevamos proves that the Perush here is like I said. It seems that in Eruvin, Meshulashim is unlike here and unlike in Makos.

Poskim

Shulchan Aruch (OC 691:6): If one put in the Megilah three threads of sinews, it is Kosher, as long as they are Meshulashim. Because there are different explanations, one must fulfill all of them, and do three stitches at the top, three at the (bottom) end, and one stitch at the quarter on each end.

Beis Yosef (DH v"Havi): If one will be concerned for the Rambam's opinion (in addition to that of the Rif and Rosh), one must make 11 stitches.

Mishnah Berurah (21): The Chayei Adam says that if it is entirely sewn with sinews, we are not concerned for the number of stitches.

` Rema: If he does not have more sinews than for this, it is better to sew the rest with linen stitches than to leave it unsewn.

Gra (27): This is like we find in Bava Basra 162b (blank lines between the text and the signatures disqualify a document, but if the blank lines were filled with Pasul signatures, it is valid. The law of Sechach supports this. Three Tefachim of air disqualify a Sukah. If one put Pasul Sechach there, it is Kosher, for its Shi'ur to disqualify is four Tefachim.) This is because it must be totally sewn from end to end to be one Sefer, except for a remnant at the end.

Rema: If he has enough sinews, he sews it entirely with sinews.

Gra (28): (If he put in three stitches of sinews,) it is Kosher. This connotes that this is b'Di'eved.

Shulchan Aruch (ibid.): One must leave a remnant unsewn at the top and bottom. Any amount suffices.

Beis Yosef (DH v'Tzarich): The Gemara requires this for a Sefer Torah. This is so it will not tear. The Mordechai (Megilah 795) wrote 'I am unsure whether one must leave a remnant in a Megilah like in a Sefer Torah. Presumably, one must.

Levushei Serad (13): If there is no remnant, a Sefer Torah can tear when rolling it closed. This is no concern in a Megilah, which has only one roller. The Mordechai was unsure if we distinguish, for other laws of a Megilah are like a Sefer Torah.