One may go out on Shabbat with a locust egg, and with a fox tooth, and with a nail from the crucified, for the purpose of healing; this is the statement of Rabbi Meir. The Rabbis prohibit using these remedies even during the week, due to the prohibition of following the ways of the Amorite. These are superstitious beliefs and the customs of gentiles from which one must distance oneself.
Many of the customs and healing practices detailed in the seventh and eighth chapters of the Tosefta of this tractate, also known as the “Amorite chapters,” are prohibited as ways of the Amorites, i.e., superstitious beliefs. Every superstitious belief, incantation, and divination falls under the rubric of several Torah prohibitions. The prohibition of divination and soothsaying comes from the verse: “There must not be found among you…a soothsayer, an enchanter, a witch” (Devarim 18:10), among others. In addition, there is the general prohibition: “And in their statutes do not walk” (Vayikra 18:3). Nevertheless, the statements of Abayye and Rava as well as those in the Tosefta are to be understood in the broadest possible manner. Any practice that was attempted and found to be an effective remedy, even if there is no clear scientific rationale for its effectiveness, may be utilized based on the empirical evidence.
Yet another example of “the ways of the Amorites” is brought by the Gemara:
One who says: I will drink and leave over, I will drink and leave over, so that his wine will increase; that statement contains an element of the ways of the Amorite.
There are variant readings of this statement. Nevertheless, there is a fundamental principle in these chapters in the Tosefta that any practice or incantation that is deemed auspicious, especially when it is stated after the fact, contains an element of the ways of the Amorites. However, any expression that contains an element of prayer or supplication is considered like any other prayer and is permitted.