Pesachim 110B

איבדור תבלונייכי, פרחא זיקא למוריקא חדתא דנקטיתו נשים כשפניות, אדחנני וחננכי לא אתיתי לגו, השתא דאתיתי לגו ⁠— קרחנני וחננכי״.

your spices, which you use for your witchcraft, should scatter; the wind should carry away the fresh saffron that you witches hold to perform your witchcraft. As long as I was shown favor from Heaven and you showed me favor, I did not come here. Now that I have come here, your favor toward me has cooled and you should find favor.

במערבא לא קפדי אזוגי. רב דימי מנהרדעא קפיד אפילו ארושמא דחביתא. הוה עובדא ופקע חביתא. כללא דמילתא, כל דקפיד ⁠— קפדי בהדיה, ודלא קפיד ⁠— לא קפדי בהדיה, ומיהו למיחש מיבעי.

The Talmud relates that in the West, Eretz Yisrael, they were not particular with regard to pairs. Rav Dimi from Neharde’a was particular about pairs even with regard to the signs on a jug; he would not write pairs of symbols on a jug. There was an incident in which there were pairs of symbols on a jug and the jug burst. The Talmud concludes: The rule of the matter is that all who are particular about pairs, the demons are particular with him; and if one is not particular, they are not particular with him. However, one is required to be concerned about the harm that might result from purposely performing actions in pairs.

כי אתא רב דימי, אמר: שתי ביצים, ושתי אגוזין, שתי קישואין, ודבר אחר ⁠— הלכה למשה מסיני. ומסתפקא להו לרבנן מאי ניהו דבר אחר, וגזור רבנן בכולהו זוגי משום דבר אחר.

When Rav Dimi came from Eretz Yisrael to Babylonia, he said: With regard to two eggs, two nuts, two cucumbers, and another matter, there is a halakha transmitted to Moses from Sinai that they are dangerous in pairs. But the rabbis are uncertain about what the other matter is, and therefore the rabbis decreed that all pairs are prohibited due to that other matter.

והא דאמרן עשרה, תמניא, שיתא, ארבעה אין בהן משום זוגי, לא אמרן אלא לענין מזיקין. אבל לענין כשפים ⁠— אפילו טובא נמי חיישינן.

And the Talmud notes that that which we said above, that the numbers 10, 8, 6, and 4 do not cause the danger associated with pairs, we said only with regard to harmful spirits. However, with regard to witchcraft, we are concerned even with regard to one who performed an activity a greater number of times.