Believing in superstitions:
The prohibition of Nichush: It is Biblically forbidden due to the prohibition of “Lo Sinacheish” for one to practice superstitions such as to say that if a black cat crosses his path then he will not leave his house that day due to belief that something bad will happen to him. [Some Poskim rule that the prohibition of Lo Sinachesh only applies when one verbalizes the superstition. However, it is permitted and even praiseworthy for one to believe and practice superstitions that the general populace believes in even if it has no source in Sefarim and the words of our sages. Other Poskim, however, negate this assertion and rule that the prohibition applies even if one does not verbalize the superstition, and simply practices it. Nonetheless, despite the above debate, practicing superstitions can transgress the prohibition of Darkei Emori, as explained next.]
The prohibition of Darkei Emori: Darkei Emori is literally defined as the ways of the Emorites. The Torah prohibits a Jew to follow the paths of the Emorites, which refers to the performance of actions that have no logic behind them and towards what they are desired to accomplish. This prohibition is possibly rooted in one of several negative commands such as “Bechukoseihem Lo Seleichu”, and “Lo Sinacheish” and practices of Avoda Zara, and Kishuf/sorcery. [The prohibition of Darkei Emori applies to actions that have no seeable benefit, and logic or understanding and were possibly originated by idolaters, however, those actions that are done as a symbol and representation of a certain matter and which was never originated for the sake of idolatry are permitted to be adapted by Jews even if it originated from gentiles.]
Superstitions permitted and/or enacted by the sages: Despite the above prohibition against believing in superstitions, and doing actions that have no scientific value for the sake of a certain purpose, nevertheless, we find numerous examples of superstitious matters that either we are allowed to believe in, or that we are even instructed to believe in and avoid. For example, the Talmud and Poskim rule that it is permitted to believe and practice mystical healing, such as to rest the tooth of a dead fox on a person to help him fall asleep. Examples of superstitious matters that we are commanded to believe in and are part of practical Halacha today that we must be careful in are too much to number, and are enumerated in various Sefarim, including the Talmud, Sefer Chassidim, Shulchan Aruch, Shulchan Aruch Harav, and many Sifrei Achronim. The basic premises behind many of these laws which are based on nonscientific dangers and worries relates to worries of demons and evil spirits and other spiritual dangers that cannot be seen by the naked scientific eye. These superstitious practices that we are instructed to believe in and follow, do not transgress any of the above prohibitions, being that they are not based on the customs of idolatry and superstitions of Gentiles, and have spiritual basis for worry as understood by our great sages. Nonetheless, we sometimes find superstitious practices that were enacted by the sages without any reason of danger whatsoever, neither physical or spiritual, and were simply done to instill fear onto the people. Furthermore, some Poskim rule that it is permitted and even praiseworthy for one to believe in superstitions that the general populace believes in even if it has no source in Sefarim and the words of our sages, as the prohibition of Lo Sinachesh only applies when one verbalizes the superstition, as stated above. Accordingly, we find many superstitious practices that are followed by different Jewish communities [i.e. Moroccan Jewry, Hungarian jewelry, etc] despite not having any source in Jewish literature and being followed even amongst Gentiles, and their Christian neighbors.
Minhag Yisrael Torah Hi and Minhag Nashim Zekeinos: A Jewish custom is considered Torah even if it does not have an explicit source in Jewish literature, and the same applies regarding traditions passed down through Jewish mothers throughout the generations. Such customs, even if superstitious in nature, are permitted and even encouraged to be followed, and are not suspected to transgress any Torah prohibition.
B. The law:
Obligation to research the source: Following a superstitious practice can at times transgress the prohibition of Lo Sinacheish and/or Darkei Emori, and at times not be under any transgression, depending on the source of the superstition and its reason. Many superstitious defined practices are indeed sourced in Jewish law and are obligatory to be followed. Furthermore, there exists superstitious defined practices which are not sourced in Jewish law but are part of classic Jewish tradition and have the status of Minhag Yisrael Torah Hi. Accordingly, since there are many Halachic restrictions which can be defined as superstitious which are an obligation to follow or at least sourced in classic Halachic literature or Jewish tradition and therefore may be followed, therefore when hearing from Orthodox Jews of a certain adherence that is kept which sounds like a superstitious belief, one is to first verify if the custom is recorded in classical Jewish works, and has the backing of Halacha. If there is no source for it in Jewish literature, then one is to research if it is a classical Jewish custom kept by traditional G-d fearing families, and therefore is subject to Minhag Yisrael.
No source-May or must one keep it: If the adherence does not have any source in classic Jewish literature [i.e. Talmud, Shulchan Aruch, traditional Achronim] then even if it can be proven to be sourced in Minhag Yisrael, one who did not receive the tradition in his family, is not required to follow the custom, and may choose to ignore it, and so is suggested. If he desires to follow it anyways, then this matter enters into the question and debate of whether following such practices are prohibited due to Darkei Emori and/or Lo Sinacheish, as explained above in A, or if it is a justifiable Jewish custom that has the status of “Minhag Yisrael Torah Hi”, and practically he is to contact a Rav. Those who received a tradition in their family and the tradition is a Minhag Yisrael kept by other families as well, are to try to abide by it under the basis of Minhag Yisrael Torah Hi, and Minhag Nashim Zekeinos.
· Many superstitious beliefs and restrictions are indeed based on Torah sources, while others are not but are nonetheless permitted to be followed if they are a Jewish tradition, while others may transgress Darkei Emori and/or Lo Sinacheish. Accordingly, one should not adapt to following superstitious beliefs that have no source in Torah literature or Minhag Yisrael.
· Regarding superstitious beliefs that have a status of Minhag Yisrael, one has no obligation to take upon himself the practice of these beliefs if they are not obligatory according to Halacha, and are not part of his personal family tradition.
· One who wishes to adapt a superstitious belief that is not for certain considered part of classic Minhag Yisrael or desires to break from a superstitious belief that is in his family tradition, is to speak with a Rav.
 See Michaber Y.D. 178-179; Rambam Avoda Zara 11; Sanhedrin 65a; Encyclopedia Talmudit Erech Darkei Haemori Vol. 7
 See Michaber Y.D. 179:3; Rambam Avoda Zara 11:4; Sanhedrin 65a
 Shiltei Hagiborim Avoda Zara 9a, brought in Pischeiy Teshuvah 179:3; Possible understanding of Rama 179:3, as initially explained in Taz 179:2
 Poskim ibid; See Yerushalmi Terumos 8:3 that one needs to suspect for that which people worry of danger; Sefer Chassidim 261 that there is danger involved in matters that people believe to be dangerous; Minchas Yitzchak 9:8
 Conclusion of Taz 179:2; Implication of Tosafos Bava Metzia 27b
 See Rama Y.D. 177:1; Admur 301:33; Mishneh Shabbos 67a
 See Rashi on Mishneh Shabbos 67a
 See Rama 177:1 “This is only forbidden if the clothing of the gentiles are worn by them for sake of frivolity [pritzus] or it is a gentile custom that has no logic behind it, as in such a case there is room to suspect that the custom derives from the Emorite customs, and that it derive from practices of idolatry passed down from their forefathers.”; See Kapos Temarim Yuma 831 and Chavos Yair 234 that Darkei Emori applies towards practices that the gentiles developed as a result of idolatry, that they believed that these actions invoke their G-ds to give assistance.
 See Minchas Yitzchak 6/80 that Darkei Emori was prohibited due to that the Emorites innovated the practices based on Kishuf.
 See Rama Y.D. 178:1 “This is only forbidden if the clothing of the gentiles are worn by them for sake of frivolity [pritzus] or it is a gentile custom that has no logic behind it, as in such a case there is room to suspect that the custom derives from the Emorite customs, and that it derive from practices of idolatry passed down from their forefathers.”; Maharik 88; See Kapos Temarim Yuma 831 and Chavos Yair 234 that Darkei Emori applies towards practices that the gentiles developed as a result of idolatry, that they believed that these actions invoke their G-ds to give assistance. See also Ran on Shabbos 67a; See Admur 301:33 “Any medical treatment that works in accordance to Segulah [i.e. supernatural causes] rather than natural cause and effect [i.e. scientifically based] does not contain the prohibition of Darkei Emori so long as it is recognizable [to the onlookers] that it’s intent is for the sake of healing”; See Igros Moshe E.H. 2/13; Y.D. 4/11-4; O.C. 5/11-4
 Admur 301:33; Michaber 301:27; Mishneh Shabbos 67a
 See Gittin 67b and onwards; Nidah 17a; Pesachim 112 Chofetz Chaim in Likkutei Halachos Niddah ibid; Divrei Yatziv 2:16; See Hakashrus 18:11-14
 The Tzava’ah of Rav Yehuda Hachassid, as well as many of his rulings in Sefer Chassidim, are filled with restrictions that can be defined as superstitious beliefs, such as for example the restriction against closing up a window.
 See Michaber and Rama Y.D. 116:5
 See Admur Hilchos Shemiras Haguf Vihanefesh
 See Kaf Hachaim Y.D. Chapter 116 and Sefer Shemiras Hanefesh for a compilation of hundreds of restrictions that are followed due to worry of danger and the like without any scientific basis.
 In other words, the same way there exists a field of science in the physical world which affects the value we attribute to actions and their expected effects, so too there is a field of science in the spiritual worlds which regular scientists are completely ignorant in, and is a field which only the greatest of our sages of the previous generations had expertise.
 See Taz Y.D. R116:4 and Darkei Moshe 116:9 in name of Geonim regarding the Tekufa
 Shiltei Hagiborim Avoda Zara 9a, brought in Pischeiy Teshuvah 179:3; See Yerushalmi Terumos 8:3 that one needs to suspect for that which people worry of danger; Sefer Chassidim 261 that there is danger involved in matters that people believe to be dangerous; Minchas Yitzchak 9:8
 Such as not buying items for a child before he is born, or for a child not to look at a mirror until his teeth have grown, or not to step over a child lest he not grow anymore, or not eating the ends of the bread. [See Teshuvos Beir Moshe; Minchas Yitzchak 9:8]
 See Admur 180:6 [not covering knife on Shabbos]; 432:11 [scattering 10 pieces of bread]; 452:4 [Hagalah]; 494:16 [Dairy on Shavuos]; M”A 494:6; Tosafus Menachos 20b
 See Rashba 1:9; Heishiv Moshe 13; Aryeh Dbei Ilai Y.D. 19
 See Beir Moshe 8:36 [regarding a) baby in front of mirror; b) stepping over a child c) wearing a red string]; Minchas Yitzchak 9:8
 Rav Eliyahu Landau wrote to me regarding purchasing baby items prior to birth, and that on this it states, “One who is not Makpid -Lo Kapdinan”, and that so is the custom that he witnessed.
 See Hiskashrus 857 that the Rebbe vehemently opposed the custom of the red string against Ayin Hara as transgressing Darkei Emori
 This follows the famous ruling of the Rashba [See Rashba 1:9; Heishiv Moshe 13; Aryeh Dbei Ilai Y.D. 19] that the Minhag of women is holy and is to be abided. [Heard from Rav Leibel Groner who is of the opinion that one should guard this custom]