In his autobiography I Am Not Spock, Leonard Nimoy wrote that he based the Vulcan Salute on the Priestly Blessing traditionally performed by Jewish Kohanim (priests) with both hands, thumb to thumb in this same position, representing the Hebrew letter Shin (ש), which has three upward strokes similar to the position of the thumb and fingers in the salute. The letter Shin here stands for Shaddai, meaning “Almighty (God)”. Nimoy wrote that when he was a child, his grandfather took him to an Orthodox synagogue where he saw the blessing performed and was very impressed by it.
The accompanying spoken blessing, “Live long and prosper“ is similar to common Middle Eastern greetings (Salaam alaykum in Arabic and Shalom aleichem in Hebrew), meaning “peace be upon you”, and its reply, “upon you be peace”. An even more ancient variation can be found with the Ancient Egyptians: the blessing ankh wedja seneb, usually translated as “may he live, be prosperous, be healthy.” William Shakespeare’s Romeo and Juliet contains the line, “Live and be prosperous.” (wiki)