What's the origin of the Israeli flag?

IFCJ

The flag of the State of Israel was largely the design of David Wolfsohn, who succeeded Theodor Herzl as president of the World Zionist Organization, a group that seeks to establish a home for the Jewish people in Israel that is secured under public law. 

The flag was introduced in 1891 as a symbol of the Zionist movement. Wolfsohn wanted to create a flag that would capture the essence of the problems faced by the Zionist movement and the Jewish people in the decades before the Jewish state was brought into being in 1948.
He decided to mirror the traditional design of the tallit, the Jewish prayer shawl, represented by two blue bars on a white background. Placing the Star of David between the blue bars completed the symbolism of the Jewish people and their struggle for national identity. 

The flag that Wolfsohn designed was first displayed in Basel, Switzerland in 1897 at the First Zionist Congress, and was officially adopted as the symbol of the State of Israel in 1948.

http://blog.ifcj.org/post/israel-101-whats-origin-israeli-flag