Although the Sages forbade going outside with an amulet on Shabbat, lest it be removed and the person will carry it in the public domain, the Mishna taught that “an effective amulet” can be worn, since it will not be removed. The Gemara on today’s daf attempts to clarify how we define “an effective amulet.”
The Sages taught in the Tosefta: What is an effective amulet? It is any amulet that healed one person once, and healed him again, and healed him a third time. That is the criterion for an effective amulet, and it applies to both a written amulet and an amulet of herbal roots; both if it has proven effective in healing a sick person who is dangerously ill, and if it has proven effective in healing a sick person who is not dangerously ill. It is permitted to go out with these types of amulets on Shabbat.
An amulet is a magical charm to protect from harm the one who possesses it or wears it. The inscriptions on amulets in ancient times appear to have been various biblical passages that spoke of healing or protection. In the practical Kabbalah, various combinations of divine names are used for the writing of amulets on parchment.
Despite the strong biblical opposition to magic and divination, amulets were accepted by the Sages, who even permitted effective amulets to be carried on the Sabbath when carrying objects in the public domain is normally forbidden. The Rambam, a rationalist thinker, rejected any belief in the amulet’s efficacy. Nevertheless he codified this rule in his Mishneh Torah (Sefer Zemanim, Hilkhot Shabbat 19:14) but he believed that it is only permitted because of the psychological relief it can offer to the disturbed mind.
Throughout the ages many rabbis not only tolerated the use of amulets but actually wrote them themselves.