Shabbat 52 - What may an animal wear on Shabbat
The Torah prohibited one to work his animal on Shabbat, by saying " On Shabbat don’t do anything that constitutes work, you, your son, your daughter,… and your animal ." Therefore, one cannot make his animal carry a load. If so, how can it graze, being that this is a prohibited labor of reaping? - The animal should be at ease, and restraining it would cause pain. Accordingly, the following rule tells us what constitutes not a burden, but normal animals’ wear and can therefore be worn by animals on Shabbat.
A camel may wear a halter - a rope that is used to control it. All animals that normally wear a collar may go into a public area on Shabbat while wearing.
Incidentally, if one needs to sprinkle the animal with the ashes of a red heifer, to remove the impurity of the dead, one needs not take the collar off. So too, if he needs to immerse the animal, he may keep the collar on.
However, we know that only humans can become ritually impure, and that the laws of ritual impurity do not apply to animals at all. - It is the collar that became impure and requires purification. But even so, it is an animal’s collar, not a utensil used by people, and the Torah talked about impurity only for utensils in people’s use!? - This collar was initially made for humans, and then re-used for an animal.
Art: Jean-Léon Gérôme - Camels at a Watering Trough