Kitzur Shulchan Aruch, Rabbi Shlomo Ganzfried
Chapter 166 : Prohibition of Omens and Auspicious Times
It is written, "You must not practice superstition nor attribute significance to [auspicious] times." What constitutes superstition? He who says, "Since the bread fell from my mouth;" or "The cane fell from my hand;" or "My son called me from behind;" "A raven croaked at rne;" "A deer crossed my path;" "A snake passed on my right;" "A fox passed on my left, therefore, I will not go on this journey because I will not be successful." Similarly, those who on hearing the chirping of a bird, say: "May it mean this and not that;" "(Now I know) it is good to do this, or it is bad to do this;" Similarly, when asked to repay a loan, he says: "Please leave me alone for now it is morning, and I do not want to start the day by making a payment;" or "It is the close of the Shabbos;" or "It is the New Moon." Similarly those who say, "We must slaughter this rooster because he crowed in the evening;" or "This hen (should be slaughtered) because she crowed like a rooster." Everything similar to these things, are forbidden. Anyone who practices any of these things, violates a negative command. Some poskim say that if you do not state the reason why you ordered the slaughter of the hen or the rooster, but simply say, "Slaughter this hen" or "This rooster," it is permissible to slaughter them, and such is the prevailing custom.
Although no superstition may be practiced through a house, a child, and a woman, they may be regarded as omens. For example, if someone built a house, or had a child born to him, or taken a wife, and afterwards he was successful on three occasions, or was unsuccessful, he may regard this as an omen for the future, and say: "This house brings me good luck" etc. It is also permitted to inquire of a child about the verse he studied (that day), and rely on it to do a certain thing, for it is regarded somewhat like a prophecy. Some Poskim say it is permitted to designate a sign for the future (and to act accordingly): as Eliezer the servant of Abraham, or Yonason the son of Saul; while other Poskim forbid it5 However, he who walks in integrity; "And trusts in God, kindness surrounds him."
What is meant by "auspicious times?" One who believes in astrology and thus says, "This day is good and this day is bad;" or this day is a good day to do this work; or this year or this month is bad for such and such a thing. Regarding our custom to hold marriages only on the days when the moon, progresses to its fullness, this is not considered superstition or auspicious, for this is done only as a favorable sign, as the coronation of Kings which were held at springs to symbolize the permanency of his rule. Similarly, it is a good sign to make a wedding on a day when the moon (progresses) to its fullness. Nevertheless it is not proper to postpone a wedding on this account, and needless to say, you should certainly not make the wedding when the bride is menstrually unclean, on the account of this custom. It is also customary to begin to study on the New Moon. The custom of not starting anything on Monday or Wednesday, is permissible according to some authorities.
Our Rabbis, of blessed memory, also said, "What is meant by meonein? It refers to one who deceives the eyes. [a magician] In other words, it is as though he holds peoples' eyes and closes them, for he deceives them. It seems to them as though he is performing wondrous, supernatural feats, while in reality he is doing nothing, but with slight of hand and cunning, he deceives them. The entertainers who perform these things at weddings, are violating a negative command. He who engages them, is guilty of transgressing (the negative command), "Before the blind you shall not place a stumbling block." Therefore whoever is able to prevent this, is obligated to prevent it. And it is certainly forbidden to view these things but if a non-Jew performs these things, it is permitted to view it.
It is forbidden to consult sorcerers unless there is danger to human life, or if someone fell ill due to witchcraft, or some mishap or evil spirit, then he is permitted to be cured by a non-Jewish sorcerer.