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Over the millennia that Jews have spent in the diaspora, they have attached Jewish meanings to the folk customs of the peoples around them. Many wedding customs that Jews observe today have this dualistic heritage.

One of the most widespread ancient beliefs is that demons or evil spirits attack individuals, especially at times of joy such as marriage or childbirth. The belief in demons was almost axiomatic in talmudic times, and traces of it still linger. In 1966, Israel's former chief rabbi, Ovadiah Yosef, made the following pronouncement: "One must not walk alone in an unpopulated place because demons dwell there."

One of life's happiest moments, the wedding night, was thought to infuriate the evil spirits. Thus, many marriage customs were created to protect the nuptial couple. Veiling the bride, traditionally explained in Genesis 24:65 when Rebecca "took her veil and covered herself" on first meeting Isaac, probably originated with protection against the kaynin hora (evil eye).

Demons were thought to be particularly frightened by fire and light. Unsurprisingly, wedding processions in many ancient cultures featured lamps, candles or torches. In Jewish weddings today, two candles are often carried with the explanation that the numerical value of ner, Hebrew for candle, when doubled, has the same value as the biblical phrase "Be fruitful and multiply" (Gen. 1:28).

The chuppah (bridal canopy) is a traditional part of most Jewish weddings. The Bible refers to a bridal bower in which the newlyweds were confined at the end of the wedding ceremony. By the Middle Ages, it had evolved into a cloth or other covering that was spread over the bridal couple to protect them from demonic assault.

Smashing a glass at the conclusion of a Jewish marriage ceremony is said to recall the destruction of the Temple in Jerusalem. Smashing of glasses or dishes was a common magical gesture throughout the Near East, where it symbolized smashing the powers of demons and other ill-wishers.

In medieval Germany, the marriage glass was often thrown against the traustein (marriage stone), a special stone embedded in the northern outer wall of the synagogue. Demons were traditionally believed to come down from the north; smashing glass in their faces was a powerful antidote.

Most of these customs, of course, sprang from superstition, and Jews were traditionally admonished against superstition. But the prevailing attitude of medieval European Jews is probably best summarized by the Sefer Hasidim, The Book of the Pious. This popular 13th-century German-Jewish treatise dealt extensively with everyday Jewish life:

"One should not believe in superstitions," read the text. "But it is best to be heedful of them."