History of Design: The flag of The State of Israel includes two blue stripes on white background with a Shield (Star) of David (in Hebrew: Magen David) in the center. This design was first displayed in Rishon-LeZion in 1885 and was also used at the First Zionist Congress in 1897 (Encyclopaedia Judaica, 1971). It was inspired by the tallit (the prayer shawl with blue stripes worn by Jews during prayer) as a symbol. The Star of David is a common symbol of the People of Israel from Biblical times. The flag was adopted officially on October 28, 1948 (25 Tishre, 5709) by the Speaker of the Provisional Council of State.
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The Magen David is a symbol of the two blood covenants!
When the Hebrews placed the blood of the paschal lamb on the side posts and lintel it formed a triangle pointing up to G-d. When Yeshua hung on the cross He formed a triangle pointing from G-d to man!
Psalm 118:23 This is the LORD's doing; it is marvellous in our eyes.
Do you know when the symbol was first used? Presumeably no earlier than Davids time.