The Vulcan salute is a hand gesture consisting of a raised hand, palm forward with the fingers parted between the middle and ring finger, and the thumb extended. Often, the famous line, "Live long and prosper", is said after it. The salute was devised and popularised by Leonard Nimoy, who portrayed the half-Vulcan character Mr. Spock on the original Star Trek television series in the late 1960s.
In his autobiography I Am Not Spock, Nimoy wrote that he based it on the Priestly Blessing performed by Jewish Kohanim with both hands, thumb to thumb in this same position, representing the Hebrew letter Shin (?), 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. There he saw the blessing performed and was very impressed by it.
The accompanying spoken blessing, "Live long and prosper" (Dif-tor heh smusma in Vulcan language as spoken in Star Trek: The Motion Picture) also appeared for the first time in "Amok Time", scripted by Theodore Sturgeon. The less-known reply is "Peace and long life." This format 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."