There are four distinct references to Shvuot in the Torah, in the books of Deuteronomy, Numbers, Leviticus and Exodus, and it is called by three different names: the “Feast of Weeks”, the “Day of the First Fruits” and the “Festival of the Harvest”. According to the Torah, it is supposed to be celebrated on the day following seven times seven weeks after “the sickle is first put to the standing grain” (Deuteronomy), or alternately, after the first Sabbath following the start of Pesach (Leviticus). The rabbis eventually decided to interpret these passages as meaning that it should be celebrated 50 days after the second day of Pesach. At present this means that Shvuot is always celebrated on the 6th of Sivan, which always comes 50 days after the second day of Pesach, the 16th of Nisan. However, that is because the Jewish calendar is now calculated long in advance according to a fixed system and the two months preceding Sivan, Nisan and Iyar, are always 30 and 29 days in length respectively. In earlier times, when the start of the lunar month was decided by actual observation, Shvuot could also have come out a day or two after or before the 6th of Sivan.
There can be no doubt that Shvuot was originally intended as an agricultural festival. That is why it is called the “Day of First Fruits” and the “Festival of the Harvest”, and that is why the Book of Numbers (Chapter 28, Verse 26) states that this the day on which “you offer a cereal offering of new grain to the Lord”. The new grain in question was from the wheat harvest, which was supposed to take place around this time. But why count 50 days from the start of Pesach, which was also understood to mean the time of the start of the growth of the wheat crop, when “the sickle is first put to the standing grain”? The answer is supplied by the word, “hamsin”. Hamsin is the name of a hot wind which often blows in from the desert in the spring in the land of Israel. However, the word “hamsin” is the Arabic version of the Hebrew “hamshim”, meaning “fifty”. It was evidently believed that this hot wind might blow at any time for a period of 50 days in the spring, during which time it could easily destroy the standing grain if it blew strong enough or hot enough. In short, the original point of the “Feast of Weeks” was to give thanks to “the Lord” that the wheat harvest had not been destroyed and there would be lots of food to eat.
As the center of gravity of Jewish culture gradually shifted from the land to the city, a new meaning was assigned to Shvuot. This new meaning was probably first developed in the land of Israel, but it took hold with particular force in the Diaspora, where the great majority of Jews lived in an urban environment. Shvuot came to be defined as the celebration of the granting of the Torah to the Israelites at Mount Sinai. The inspiration for this innovation undoubtedly came from the 19th chapter of the Book of Exodus, which begins by stating that the Israelites “entered the wilderness of Sinai” on “the third new moon” after the exodus from Egypt. Since it was generally assumed that the Exodus had taken place in the month of Nisan, the month in which Pesach is celebrated, this passage could be interpreted to mean that the Israelites arrived in the vicinity of Mount Sinai on the 1st of Sivan. To be sure, there was a minor inconvenience in that the Book of Exodus specifically states (Chapter 19, Verse 16) that the encounter with “the Lord” at Mount Sinai started “on the third day” after the Israelites arrived, which would presumably mean the 3rd and not the 6th (or 5th, or 7th, or whatever) of Sivan. But the 3rd was close enough, and despite the absence of one single specific reference in all of Tanach to the Israelites receiving the Torah on Shvuot, the belief that they had done so became the main focus of the celebration of Shvuot in the Diaspora.
However an uneasy feeling about the true meaning of Shvuot must have persisted, because there is a clear tendency in the later history of this festival to proliferate new meanings for it. In particular, it became the custom to read the Book of Ruth on this day. I have never seen a convincing explanation of why this is so. To be sure, some of the events described in the Book of Ruth take place around the time of the end of the wheat harvest, and perhaps this was the original reason for the connection. There is no other obvious reason for it. The Book of Ruth is generally associated with two things: the famous “whither thou goest” speech by Ruth where she decides to throw in her lot with Naomi and the Israelites, and the genealogy at the end where Ruth and her husband Boaz are portrayed as the parents of the grandfather of King David. Neither of these things has any obvious connection to Shvuot. Some rabbis declare that an analogy is intended between Ruth’s “conversion” to Judaism and the acceptance of the Torah by the Israelites at Sinai. But in point of fact Ruth doesn’t actually go through a formal conversion process in the Book of Ruth but just says she is willing to accept Naomi’s God as her own. By the standards of contemporary Orthodox Judaism, and probably the Conservative and Reform as well, Ruth would not be deemed a convert, which means that King David would not have been Jewish since he had a non-Jewish great grandmother. Be that as it may, I have the strange feeling that the Book of Ruth was just thrown in there to supply more meaning to a holiday whose original meaning had more or less disappeared and whose substitute alleged meaning was open to question.
Among the Reform, the meaning of Shvuot has been further modified by its transformation into a ceremony of “Confirmation”. Children are supposed to be brought to shul (or more precisely, “temple”) on this day and “confirmed” in the Jewish faith. Whether this ceremony is intended as the equivalent of a Reform Bar or Bat Mitzvah or as something additional is unclear to me. In any case it would appear to be an extension of the same tradition which see Shvuot as a celebration of the acceptance of the Torah at Mount Sinai and/or the “conversion” of Ruth.
In actual practice, the main meaning of Shvuot today so far as I can see is that it the time you are supposed to eat cheescake, or in a pinch, blintzes. This is to commemorate entry of the Israelites into a “land of milk and honey”, although I am not too clear on what milk and honey have to do with either the wheat harvest or Mount Sinai. It would seem that mere logic is not the best tool to unravel the meaning of Shvuot. And I am leaving out other traditions, such as the one which says Shvuot is the time you are supposed to stay up all night and discuss Torah, or among secular Jews, the peace process. In short, Shvuot would seem to be a do-it-yourself holiday, which can absorb almost any meaning you care to assign to it. And we all know what it means to the average Israeli: go to the beach..