Consider Yourself Warned: Sneezing in Jewish Folklore
It is remarkable how Jewish tradition, in its careful reading of the Bible, discovers stories hidden beneath stories. Even more extraordinary is the wit to see a story lurking in a lack of story. Take illness. The first person who is described as ill is our ancestor Jacob (Gen. 48:1). This led some perspicuous Jewish reader to ask the question, "Why is this first mention of an ill person so late in the story of humanity? Could it be that Jacob is the first person to experience illness?" And that's exactly what happened. Pirkei de-Rabbi Eliezer was the first to fully develop this thought:
From the day the heavens and earth were created, no man was ever ill... Rather, in any place he happened to be, whether on the way or in the market, when he sneezed his soul left through his nostrils. [So it was] until our ancestor Jacob came and prayed for mercy concerning this, saying, Blessed Holy One, do not take my soul from me until I have blessed my sons and my household; so He accepted him, as it was said, "And it came to pass after these things that one came to Joseph and said, "Look, your father is ill."..... (PdRE 52).
Thus a sneeze, once the very act of expiration itself, comes to be understood to be an act of divine compassion, an omen that death is approaching.
This is an idea very much in keeping with the idea, rooted in the Bible (Gen. 1:26), that the spirit enters and leaves through the nose, and that all humans are pneumatically permeable, that various spirits (of wisdom [Exo. 28:3, 31:3], prophecy [Num. 11:17, 29], and woe [I Sam. 16:23]) pass easily in and out of the body, and that our very souls even leave us on a temporary basis while we sleep (the Elohai Neshamah morning prayer).
Of course, an omen can be averted with the proper ritual or words of power. And so it is that Jews came to believe it was obligatory to respond to a sneeze with a word or phrase to counteract it:
....Therefore a man is duty bound to say to his fellow who sneezes, Chayyim! [Life!] changing death in the world into light [fulfilling the promise of Scripture] as is written, "His sneezes flash forth light" (Job. 41:10)....
Other phrases evolved to keep the soul within the body, such as l'chayyim tovim [Hebrew], marpe, assuta [Aramaic], zu gesund, and gesundheit [Yiddish].
The fact that this was more than just a wish, but actually a counter spell, is made clear in arguments in the Tosefta, where some Sages worry that the blessing response may in fact be a "Way of the Amorites" [the Talmudic idiom for witchcraft] (T. Shabbat 7:5).
Over time this concern subsided and, as the medieval Pirkei de Rabbi Eliezer highlights, a blessing in response to a sneeze came to be considered mandatory.
Zal g’mor: To learn more, read the Encyclopedia of Jewish Myth, Magic, and Mysticism:http://www.amazon.com/Encyclopedia-Jewish-Myth-Magic-Mysticism/dp/0738709050