Shabbos, Chapter 5, Mishnah 3. This mishnah lists the items with which an animal may not go out on Shabbos, and it opens with the words: "U'vameh ein ha'beheimah yotze'ah" - and with what may an animal not go out.
"Lo yeitzei gamal b'mitutelet" - a camel may not go out with a mitutelet:
The mitutelet is a cushion that was placed on the camel's hump, and at times it was tied beneath its tail so that the strap around the tail would not chafe the camel. The camel may not go out with it, out of concern that it may fall off and the owner will come to carry it in a public domain. The Gemara explains, however, that if the mitutelet is tied at one and the same time both to the hump and to the tail, there is no concern that it will fall, and therefore the camel is permitted to go out with it on Shabbos.
"Lo akud v'lo ragul" - not bound (akud) and not hobbled (ragul):
Akud and ragul are two different ways of tying an animal's legs:
Akud - tying a foreleg to a hind leg. This is not a normal way of securing an animal, and therefore it may not go out this way.
Ragul - tying within a single leg itself: the leg is folded at the joint and its two parts are tied to one another.
"V'chein she'ar kol ha'beheimos" - and so too all other animals: this law is not stated regarding a camel alone, but regarding all other animals as well.
"Lo yikshor gamal zeh b'zeh v'yimshoch" - one may not tie one camel to another and pull them:
One may not tie camels one behind the other and lead them along. The problem here is not one of carrying; rather, it looks as though he is leading his animals to the market in order to sell them. But "aval machnis chavalim l'toch yado u'moshech" - he may gather the ropes into his hand and pull: a person is permitted to hold in his hand all the ropes leading to the camels and to lead them in this manner, since this is not the usual way of taking them to be sold, and it does not look as though he is leading them to the market for sale.
The Gemara adds a condition: this is permitted as long as no handbreadth of rope protrudes beyond his hand. If a handbreadth does protrude, it looks like carrying ropes on Shabbos and not merely like ropes attached to the animal.
"U'vilvad shelo yichroch" - provided that he does not wind them together:
The mishnah concludes that those very ropes leading from the camels, which he is permitted to gather into his hand, may not be wound and tied together. The reason for this is not a matter of Shabbos, but a concern of shaatnez: the camels' ropes - some are made of wool and some of linen, and when the hand grows warm from the mixture of wool and linen that have been wound and tied together, there is a problem of shaatnez, even though there is no problem of Shabbos here.
In summary: this mishnah lists the items with which an animal may not go out: a mitutelet that is not tied in two places, out of concern that it will fall and he will come to carry it; akud and ragul, which are not a normal way of securing an animal; and tying camels to one another, which looks like leading them to the market. We also saw the permission to hold the ropes in one's hand, provided that no handbreadth of rope protrudes, and the prohibition against winding the ropes together - not because of Shabbos, but because of the concern of shaatnez.