The Star of David (Heb. Magen David), a mystical symbol consisting of two superimposed triangles forming a star or hexagram; today this is regarded as a jewish symbol and known as the Jewish Star.
Although occurring in the Capernaum synagogue (3rd cent. CE), it was in ancient times predominantly a non-jewish decorative motif (e.g. on roman mosaic pavements), and is found in christian churches in the Middle Ages, while absent from contemporary jewish decoration and not mentioned in rabbinic literature: Star of David. With the establishment of the State of Israel the jewish star on the flag has also become a symbol of Israel.
A David's shield has recently been noted on a jewish tombstone at Taranto, in southern Italy, which may date as early as the third century of the common era. The earliest jewish literary source, which mentions it, is the Eshkol ha-Kofer of the Karaite Judah Hadassi (middle of the 12th cent.), says, in ch. 242: "Seven names of angels precede the mezuzah: Michael, Gabriel, etc... Tetragrammaton protect thee! And likewise the sign called 'David's shield' is placed beside the name of each angel". It was, therefore, at this time a sign on amulets.
In magic papyri of antiquity, pentagrams, together with stars and other signs, are often found on amulets bearing the jewish names of God, and used to guard against fever and other diseases. It is possible, that the kabbalah derived the symbol from the templars. Kabbalah makes use of this sign, arranging the Ten Sephiroth, or spheres, in it, and placing it on amulets.
A manuscript Tanakh dated 1307 and belonging to Rabbi Yosef bar Yehuda ben Marvas from Toledo, Spain, was decorated with a Shield of David.
In the synagogues, perhaps, it took the place of the mezuzah, and the name "shield of David" may have been given it in virtue of its presumed protective powers. The hexagram may have been employed originally also as an architectural ornament on synagogues, as it is, for example, on the cathedrals of Brandenburg and Stendal, and on the Marktkirche at Hanover.
In 1354, the jews of Prague were allowed by emperor Karl the Fourth to display a red flag on which was a six-pointed star, that later would be called the Magen David or "shield of David". In 1592, a certain Mordechai Maizel from the same city was allowed to affix to his synagogue "a flag of King David, similar to that located on the Main Synagogue". In 1648, the jews of Prague were again allowed a flag, in acknowledgment of their part in defending the city against the swedes. On a red background was a yellow shield of David, in the centre of which was a swedish star. In Hungary, in 1460, the jews of Ofen (Budapest) received king Mathios Kuruvenus with a red flag on which were two shields of David and two stars.
For kabbalists, the shield of David represents a national religious symbol connected to the End of Days, for from the descendants of David will come the Messiah. The prophet Isaiah offered six definitions of the honour to be accorded to the Messiah, corresponding to the six points of the shield of David; "And there shall come forth a rod out of the stem of Jesse, and a Branch shall grow out of his roots: And the spirit of the Lord shall rest upon him, the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and of the fear of the Lord"; (Isaiah 11:1-2).
Moreover, the shield of David suggests the four directions of the compass: north, south, east and west, the heavens above and the earth beneath. These accord with the number of points on the star, with God in control of them all.
The shape of the star is an example of the hexagram, a symbol which has significance for other belief systems. The hexagram pre-dates its use by jews. Its most prevalent usage outside of judaism was and is the occult. Some orthodox jewish groups reject the use of the hexagram because of its association with "magic" and the "occult". Yet the star of David remains an important symbol within legitimate jewish mysticism and the Kabbala. Some Haredi groups, such as Neturei Karta, reject it because of its association with Zionism.
Many modern orthodox synagogues, and many synagogues of other jewish movements, have the israeli flag with the star of David prominently displayed at the front of the synagogues near the ark containing the Torah scrolls. The star of David can be found on the tombstones of religious jews, going back hundreds of years in europe as it became accepted as the universal symbol of the jewish people.
Some researchers have theorized that the star of David represents the astrological chart at the time of David's birth or anointing as king. The star of David is also known as the "King's Star" in astrological circles, and was undoubtedly an important astrological symbol in Zoroastrianism.
Prof. Gershom Sholem theorizes that the "star of David" originates in the writings of Aristotle, who used triangles in different positions to indicate the different basic elements. The superposed triangles thus represented combinations of those elements. From Aristotle's writings those symbols made their ways into early, pre-moslem, arab literature. The arabs were very interested in arithmetics, and were also very strongly drawn to occult and demonic tales. In fact, one of the most important personae in early arab literature was king Salomon (Suliman). The Babylonian Talmud contains a legend about king Salomon being kidnapped by Ashmedai, the king of demons. He succeeded in kidnapping the king by stealing his "seal of Salomon" - (arabic - Hattam Soliman), although according to the Talmud this seal was simply a metal coin with hebrew letters meaning the name of God, inscribed on it. It is possible that the seal was altered in the arab tales.
The first apparition of the symbol in jewish scriptures was in oriental kabbalistic writings, so it is possible that it was an alteration of the pentagram under arab influence. Early jewish symbols include the Shofar ("ram's horn"), Lulav ("shoot of palm"), and the seven-branch Menorah ("candelabra"), but no hexagram is found in early jewish symbolism.