What is the significance of asking what they tied for the Mishkan?

Ha'Boneh: This hints to the clinging of the Shechinah to Yisrael, and how careful one must be so it will persist among them.

What are the tent pegs?

Rashi: They inserted pegs in the ground - "Yisdos ha'Mishkan." They tied the curtains to them via Meisereihem.

Rav Elyashiv: We should have asked, this did not require a professional knot! The Rambam (Hilchos 10:1) obligates only for a professional knot! The Rema (317:1) holds that any double knot is considered professional, for it is tight and strong. if so, the Gemara's question includes that since it was in order to untie, presumably, it was not professional.

What is difficult if the tying was with intent to untie?

Rashi: Any knot that is not permanent, one is exempt for it (113a)!

Rav Elyashiv: Above (31b), we said that Soser is liable only with intent to build in the same place. Even though they rebuilt the Mishkan elsewhere, since it was Al Pi Hash-m, it is considered the same place. For the same reason, building the Mishkan was considered permanent. if so, also the knots should be considered permanent! (NOTE: This is in the Havah Amina that they tied to tent pegs, so when Hash-m commanded to travel, this included a command to untie now and retie later. - PF) it seems that tying must be truly permanent. (However, the Yerushalmi compares tying to building.) Surely, one who ties for a period of time, e.g. a week or month, even if he intends to untie it later, it is considered permanent and he is liable for it. if so, what was the question? They did not know when Hash-m will command to travel - perhaps it will be after a while! We must say that a knot that is Safek Shel Kayama, it is like Einah Shel Kayama, and he is exempt for it. Beis Meir asked, if they camped close to Shabbos, surely they would not travel again before Motza'ei Shabbos. i say, Hash-m did not burden them to camp close to Shabbos.

Rav Elyashiv: the Yerushalmi compared tying to building. Why do we conclude that one is liable for temporary building, but not for temporary tying? The primary building in the Mishkan was erecting it. Therefore, even temporary building is liable. Tying is tightly joining objects - presumably, it is only if this is permanent. Building is making a place proper for a house or Mishkan; it is used. One does not use the tying, just it prevents [bonds from softening, and] matters from separating. if it is temporary, a knot is not needed - a bow suffices, for it need not be tight! Acharonim ask, the opinion that the Mishkan was considered permanent (since they traveled Al Pi Hash-m) should be able to learn from the pegs. Our Gemara rejected this. i say that since the pegs are not for the Mishkan itself, just a Machshir, the permanence of the Mishkan does not help for them.

We should have asked, we should learn from here that tying with intent to untie should be liable!

Rav Elyashiv citing Shirei Korban (Reish Perek 15): Just like Hotza'ah is an inferior Melachah, so it needed a verse "Al Yetzei", so tying with intent to untie would need a verse.

Rav Elyashiv: Hotza'ah needs a verse and a tradition from Sinai to distinguish Reshus ha'Yachid from Reshus ha'Rabim. Why should tying need a verse?

Rav Elyashiv: in Bava Kama (2a) we say that [an Av Melachah] must be in the Mishkan, and important. Chachamim were authorized to decide what Avos and Toldah to learn from the Mishkan. The Gemara understood that it is not proper to be liable for tying with intent to untie. it is not clear whether Meleches Kosher is due to tightly joining the objects, or due to man's action.

What is the meaning of 'two tied threads were together'?

Rashi: They were next to each other.

What is the meaning of 'he unties one and ties one'?

Rashi: After they were woven, he unties one, for they jut out and are seen, and he leaves the other tied.

Tosfos: (73a, citing R. Chananel): He unties the knots, discards the string in the middle, and ties the two remaining ends together.

Rav Elyashiv: Rashi did not explain so, for also in Yoma 47a and Pesachim 75b it says 'this is not proper for a mortal king', and there it discusses Avodah, not mere preparation for Avodah. if a worm ate a hole in a board, they melted lead into it to fill it, even though in the place of wealth (Hekdesh), we do not conduct like paupers (102b)! Rashi (DH Hashta) holds that in the conclusion, they tied for the curtains, but did not untie. He says (111b) that we learn tying from the curtains, for he holds that it must be permanent; the Chilazon nets were not permanent. They were made to be permanent - we could not learn untying from temporary knots - but in practice they were not permanent. R. Chananel holds that they did not even tie for the curtains - it is improper even for a mortal king.

Why is this improper for a mortal king?

Rashi: When he unties it, a hole is seen in the curtain. The threads were six-fold; they were thick. They were careful - if two tied threads were close together, they tie one, and cut the other above and below, and connect them via a long thread, and tie above and below. Now, there are not two tied knots near each other.

Why did they trap the Chilazon?

Rashi: it is to dye Techeles with its blood. it is like a small fish; it comes up once in 70 years.

Rav Elyashiv: The Chilazon is in Zevulun's portion, in the north of Eretz Yisrael. it is not in the Midbar! Perhaps primarily it is there, but they were made available for Yisrael in the Midbar, when they were near Yam Suf; Radvaz (2:685) says so. The Rambam learns like this; Kesher must be permanent. Or, we learn Melachos that were proper to do to for the Mishkan, even if in practice they were not done in the Midbar. The Rif learns like this; he requires a professional knot, but it need not be permanent.

Why would they tie and untie knots in nets?

Rashi: The nets were made of permanent knots, Sometimes they needed to take threads from one net to add to another, so they untie here and tie here.

Tosfos: Rashi (111b) explained that sometimes they tied nets, and sometimes they untied them.