The Magen David (Shield of David, or as it is more commonly known, the Star of David) is the symbol most commonly associated with Judaism today, but it is actually a relatively new Jewish symbol. It is supposed to represent the shape of King David’s shield (or perhaps the emblem on it), but there is really no support for that claim in any early rabbinic literature. The symbol is not mentioned in rabbinic literature until the middle ages, and is so rare in early Jewish literature and artwork that art dealers suspect forgery if they find the symbol in early Jewish works.
Scholars such as Franz Rosenzweig have attributed deep theological significance to the symbol. For example, some note that the top triangle strives upward, toward G-d, while the lower triangle strives downward, toward the real world. Some note that the intertwining makes the triangles inseparable, like the Jewish people. Some say that the three sides represent the three types of Jews: Kohanim, Levites and Israel. Some note that there are actually 12 sides (3 exterior and 3 interior on each triangle), representing the 12 tribes. While these theories are theologically interesting, they have little basis in historical fact.
The symbol of intertwined equilateral triangles is a common one in the Middle East and North Africa, and is thought to bring good luck. It appears occasionally in early Jewish artwork, but never as an exclusively Jewish symbol. The nearest thing to an “official” Jewish symbol at the time was the menorah.
In the middle ages, Jews often were required to wear badges to identify themselves as Jews, much as they were in Nazi Germany, but these Jewish badges were not always the familiar Magen David. For example, a fifteenth century painting by Nuno Goncalves features a rabbi wearing a six-pointed badge that looks more or less like an asterisk.
In the 17th century, it became a popular practice to put Magen Davids on the outside of synagogues, to identify them as Jewish houses of worship in much the same way that a cross identified a Christian house of worship; however, I have never seen any explanation of why this symbol was chosen, rather than some other symbol.
The Magen David gained popularity as a symbol of Judaism when it was adopted as the emblem of the Zionist movement in 1897, but the symbol continued to be controversial for many years afterward. When the modern state of Israel was founded, there was much debate over whether this symbol should be used on the flag.
Today, the Magen David is the universally recognized symbol of Jewry. It appears on the flag of the state of Israel, and the Israeli equivalent of the Red Cross is known as the Red Magen David.
via Judaism 101: Signs and Symbols – Mozilla Firefox.
Curiously, the Great Seal of the United States appears to contain an image of a Star of David. At the top of the obverse side of the Great Seal is a cluster of thirteen stars shaped in a very obvious “Star of David” shape, consisting of 13 smaller American Stars probably symbolizing the 13 original colonies, above the eagle’s head. This image is also found on the reverse side of the U.S. one dollar bill. No-one is absolutely sure today why that is so. Some historians think it was a way of showing gratitude to Haym Solomon (1740-1785) who was Jewish and is acknowledged as the prime financier of the American side during the American Revolution and the American Revolutionary War of 1776, which many are not aware of. Some maintain Solomon designed the great seal himself.
Another reason has been postulated that perhaps it was a way of the Founding Fathers of the United States acknowledging the God of the Hebrew Bible because of their strong devotion to the “Old Testament” as a guide to life. Others have seen more sinister reasons that actually border on anti-Semitic conspiracy theories.
Whatever, the reasons may be, there is no question, that the shape of the Star of David is clearly emblazoned on the US’ Great Seal and on all US one dollar bills today.
– Star of David, AcademicKids.com
Six-Pointed Star, Star of Creation, Star of David –
Although ancient and symbolizing the six days of creation, best known in modern times as a symbol of Judaeism.
via Christian Symbols , Christian Glossary