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1. There is a dispute about whether a cow may go out with a strip of leather tied between its horns.
2. A cow may go out with a halter or bridle on Shabbos, if it is needed to control the cow.
3. Rebbi Yosi: Four animals may go out with reins on Shabbos.
4. A ring on an animal may be immersed in a Mikvah while the animal is wearing it.
5. A Tamei vessel can become Tahor if an action is done to significantly alter the vessel.
A BIT MORE
1. One opinion: It is always forbidden, whether the strip is for adornment or serves as a halter to control the cow, because cows are not wild animals that normally need to be controlled in this fashion. Another opinion: It is permitted if its purpose is to facilitate handling the cow.
2. Abaye: This is necessary when taking a cow on an intercity trip. Rava: This was common practice for a red heifer. Since it was very expensive, its owners would guard it carefully, including making sure it had a halter or bridle.
3. They are: A horse, mule, camel, and donkey. Rebbi Chanina remarked that the mules of Rebbi's house used to go out on Shabbos with reins.
4. Rebbi Yitzchak: Such a ring is normally Tahor. It can become Tamei only when used as a ring for a person. Rav Yosef: Such rings can become Tamei since they are used by a person to pull the animal, and therefore they are considered a utensil used by a person.
5. Rebbi Yehudah says that in order for the vessel to become Tahor, the action must damage the vessel and not merely change it for the better.
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