Shabbat 58A

אין בה משום עטרות כלות.

the rabbinic decree prohibiting adorning brides with bridal crowns to commemorate the destruction of the Temple does not apply to an istema.

ושמואל אמר: כבלא דעבדא תנן. ומי אמר שמואל הכי? והאמר שמואל: יוצא העבד בחותם שבצוארו, אבל לא בחותם שבכסותו!

Earlier, the Talmud cited R' Abbahu’s opinion that the kavul mentioned in the Mishnah, which one may not wear into the public domain on Shabbat, is a woolen cap. And Shmuel said: It is the seal of a slave that we learned about in the Mishnah. The Talmud asks: And did Shmuel actually say this? Didn’t Shmuel say: A slave may go out on Shabbat with a seal that is around his neck but not with a seal that is on his clothes? Apparently, Shmuel holds that one may go out into the public domain with a slave’s seal. How, then, could he say that kavul in the Mishnah, with which one may not go out into the public domain, is referring to the seal of a slave?

לא קשיא: הא דעבד ליה רביה, הא דעבד איהו לנפשיה.

The Talmud answers: This is not difficult. This, where Shmuel said that one may go out with a slave’s seal on Shabbat, is referring to a case where his master made it for him. The slave will not remove it because he fears his master. Therefore, there is no concern lest he carry it. However, that, where the Mishnah said that it is prohibited to go out with a kavul, which according to Shmuel is the seal of a slave, is referring to a case where he made it for himself to indicate to all who his master is so that he may enjoy his master’s protection. In that case, since it is dependent solely upon his discretion, there is concern lest he remove the seal and carry it. Therefore, the rabbis prohibited going out with it into the public domain.