Shabbos, Chapter 6, Mishnah 4. The mishnah opens with the law of going out into a public domain on Shabbos while carrying weapons: "Lo yetzei ha'ish lo v'sayif v'lo v'keshes v'lo v'seris v'lo v'alah v'lo v'romach" - a man may not go out with a sayif, nor with a keshes, nor with a teris, nor with an alah, nor with a romach. And these are what they are:
"Sayif" - a sword.
"Keshes" - a bow and arrow.
"Teris" - a shield.
"Alah" - two explanations are given: a stick or staff with a ball at its upper end, used as a weapon, a sort of war club; or a type of round shield, and according to this explanation the teris mentioned earlier is a triangular shield, from the word 'trai' (three).
"Romach" - a spear.
None of these is considered a garment, and none of them is an ornament either. Therefore, "v'im yatza chayav chatas" - one who goes out with them into a public domain has transgressed a Torah prohibition, and if he did so unintentionally he must bring a chatas offering for it.
The dispute between Rabbi Eliezer and the Sages:
Rabbi Eliezer disagrees and says: "Tachshitin hen lo" - weapons are considered a person's ornaments, and accordingly there is room to say that a man may go out with them. And there is indeed a basis for this, since in ancient times this was something people commonly did.
"V'chachamim omrim, einan ela l'gnai" - and the Sages say, they are nothing but a disgrace. Carrying a weapon is purely a negative thing. The proof is from the famous verse in Yeshayah: "V'kissu charvosam l'itim vachanisoseihem l'mazmeros, lo yisa goy el goy cherev v'lo yilmedu od milchamah" - in the future, in the days of Mashiach, swords will be beaten into plowshares and spears into pruning hooks, no nation will lift a sword against another, and they will no longer learn warfare. If a weapon were an ornament, and not a shameful necessity, it would remain even then. This proves that it is not something positive but something negative, and it is not viewed as an ornament.
The biris - it is tahor and one may go out with it:
The mishnah concludes with a matter relating to a woman's clothing and ornaments: "Biris tehorah v'yotzin bah b'Shabbos" - a biris is tahor and one may go out with it on Shabbos. The biris is a kind of ring or band that encircles a woman's thigh, whose function is to hold her stockings in place.
"Tehorah" - even though it is a utensil, it does not become susceptible to tumah, because it does not serve the person himself but rather his clothing. This is a use that serves a utensil and not a use that serves a person: it serves the garment and not the woman directly.
"V'yotzin bah b'Shabbos" - a woman is permitted to go out with it into a public domain, because it is considered part of the garment. And there is no concern here of the kind that exists in the case that follows, that she might remove it in order to show it to her friends, since by removing it her thigh would be exposed.
The kevalim - they are tamei and one may not go out with them:
The kevalim are a chain that ran between the two biriyos mentioned above, whose function was to shorten a girl's steps, so that she would walk with delicate, measured steps. At times they were made of silver and gold. The kevalim are tamei, meaning they are susceptible to tumah, because they serve the woman herself and keep her steps measured.
"V'ein yotzin bahen b'Shabbos" - and one may not go out with them on Shabbos, because of their costliness and beauty there is a concern that she will remove them to show them to her friends and carry them four amos in a public domain. For removing them does not cause any exposure, since the biriyos that hold up the stockings remain in place and there is no concern that they will fall; the kevalim are nothing more than a device to keep her steps from being too wide. Therefore a woman may not go out with them into a public domain on Shabbos.
In summary: in this mishnah we learned that a person may not go out on Shabbos carrying weapons - a sword, a bow, a shield, a club and a spear - and if he did go out he is liable to bring a chatas. Rabbi Eliezer held that they are his ornaments, and the Sages proved from the verse in Yeshayah that they are nothing but a disgrace. We also learned the distinction between the biris, which is tahor and one may go out with it because it serves the garment and there is no concern that she will remove it, and the kevalim, which are tamei because they serve the woman herself, and one may not go out with them lest she remove them to show them to her friends and carry them in a public domain.