http://dafyomi.co.il/shabbos/insites/sh-dt-061.htm2) SUMMARY: "MUMCHEH KAMEI'A" AND "MUMCHEH GAVRA"
The Gemara discusses what makes a Kamei'a (an amulet for healing) into a Kamei'a Mumcheh (one that has been proven to be effective), which one may wear in Reshus ha'Rabim on Shabbos regardless of the level of expertise of the doctor who wrote it. The Gemara also discusses what makes a doctor into a Rofeh Mumcheh (who has been proven to be an expert healer with his amulets), such that any amulet written by him may be worn in Reshus ha'Rabim on Shabbos. In order to better understand the Gemara, it is important to review several rules:
(a) There are three factors involved with giving a doctor or a Kamei'a the status of a Mumcheh:
1. the Kamei'a that was used
2. the doctor who wrote it
3. the person who was healed by it.
The Rishonim also mention a fourth factor -- which sickness the Kamei'a was intended to cure. However, this is not really an additional factor, but it is included in the first (the Kamei'a that was used). The practice was to write a different type of Kamei'a for each type of sickness, and to write the same type of Kamei'a for the same sickness. Therefore, for which sickness the Kamei'a was written is really the same as which Kamei'a was written (#1 above).
(b) The success of the cure may depend on the Mazal of the doctor, the Mazal of the sick person, or both. However, when a Kamei'a is proven effective, its success is not attributed to its Mazal but rather to the wisdom that went into writing it. The effectiveness of the doctor, on the other hand, can depend on his Mazal (RASHI 61b, DH Mazlei, and RAN there, who writes this more clearly). Thus, a doctor who is a "Mumcheh" may have propitious Mazal, while the "Mumcheh" status of the Kamei'a is determined solely by the skill and expertise involved in writing it.
(c) A Kamei'a becomes Mumcheh by successfully curing an illness three times, even if it was written by one doctor, or if it healed the same patient three times. We do not attribute the success of a Kamei'a that worked three times to the patient's Mazal or to the doctor's Mazal. Thus, if a doctor wrote one Kamei'a three times (and it was successful every time), the doctor does not become Mumcheh. The reason for this is either because the success of the Kamei'a depends on wisdom, and not on Mazal (Rashi DH Mazlei, and RAN), or because the Kamei'a is the main factor in improving the health of the sick person, since without the Kamei'a the doctor has no chance of curing the illness (RITVA). (Rashi at the beginning of the Sugya seems to contradict this when he writes that the doctor does become Mumcheh if he wrote the successful Kamei'a three times; see Insights to Shabbos 61:4.)
3) "MUMCHEH KAMEI'A"
OPINIONS: What is a Kamei'a Mumcheh? What makes it Mumcheh?
(a) RASHI says that the Mumcheh Kamei'a refers to the charm (that is, the specific script) that is written inside the amulet. Once that charm becomes Muchzak (it has worked three times consecutively), it may be written by any doctor to cure that illness, and it may be worn outside on Shabbos. According to Rashi, in order for a doctor to become Mumcheh, he must write three different successful charms. Once he has written three different successful charms, he may now write any charm, and one may wear it outside on Shabbos.
(b) TOSFOS and ROSH (6:8) disagree and say that just because a doctor knows how to write three charms is no proof that every charm he writes from then on will be successful. They therefore say that what Rashi describes as making the Kamei'a Mumcheh is actually what makes the doctor Mumcheh. A doctor who is Mumcheh, then, is one who has written one charm successfully three times. Mumcheh Kamei'a, according to Tosfos and Rosh, means that the very same amulet (that is, the actual piece of parchment itself) worked three times. Such an amulet may be worn by anyone on Shabbos. According to Tosfos, if the same text of that amulet is re-written and another amulet is made, even though it contains the same text as the successful amulet, it is considered an entirely new and different amulet.
Shulchan Aruch on Amulets:
http://www.torah.org/advanced/shulchan-aruch/classes/chapter12.htmlIt is forbidden to consult astrologers or rely on omens, but it is permissible to prefer or avoid particular days of the week or month for certain activities or to make a decision based on the outcome of an event (179:1-4). It is forbidden to use incantations to control animals or for medicinal purposes except to avoid danger (179:5-11), but it is permissible to use amulets for protection against injury or sickness (179:12). It is permissible to consult the spirits of the dead (179:13-14) but dealings with demons should generally be avoided (179:16,19). It is forbidden to practice deceptive magic or to learn from a magician (179:15,19). On the use of Divine names for supernatural purposes see 246:21.