[Judaic] The doubling of anything is a source of bad luck. According to the Talmud (Pesachim 109b 110b) activities done twice in a row or in pairs, such as eating, drinking, or copulation, invites the attention of evil spirits once the person leaves his or her home. Thus one should neither celebrate a double joy (like two weddings), or perform the same onerous act twice, such as a judge passing the same sentence, all on the same day. Even drinking from two cups, one after the other, invites ill luck or the evil eye. (B. Ber., Pes.; En Yaakov). The Book of the Great Name warns the adept not to look in the face of a twin for forty days after reading the book. Asmodeus is the demon who has power over this vulnerability. The Talmud passages explain how to mitigate this: by crossing thumbs in the palms of the opposing hands and reciting "You and I; that is three!"
PAIRS
Meaning of PAIRS in English
Encyclopedia Mythica English dictionary. Английский энциклопедический словарь греческой мифологии. 2012