Question:
There is a well-known story that the Vilnaer Gaon sz'l wished to reintroduce Birkas Kohanim in Chu'l, but a fire broke out, which made him reconsider and change his mind. (It's quoted in Shu't Meishiv Davar, amongst other reliable sources.) Why is this not Nichush, as described in Shulchon Aruch, siman Yo'd, Siman 179?
Answer:
Hello,
There are a number of opinions among the Rishonim, as to what nichush is. According to the Rambam (Avoda Zara 11-4), when a person makes a sign that, if this and this will happen, then it will happen to me in the future, it is a sign that such and such will happen (similar to what Eliezer did with Rivka).
The Raavad and others (including Rashba 1-114, Meiri, and Tur) believe that nichish applies only when it involves a “professional nichush” or a consistent sign, such as a deer crossing one’s path, which is used repeatedly, not just a one-time sign like the one Eliezer used when seeking a wife for Yitzchak. The Rema (Y:D 179-4) mentions both viewpoints.
From this, we see that if the sign appears after the fact and is a one-time occurrence, everyone agrees it is not considered nichush. However, doing this is still not advisable unless you are like the Vilna Gaon, who can interpret signs from shomayim.
Best wishes
Sources:
ע' בי' הגר"א יו"ד ס' קע"ט ס"ק י"א, מתנת משה ח"ד עמ' קל"ג -קל"ט.
