Q. Why do we decorate the Shul with plants and flowers on Shavuot?
A. The custom of decorating the Shul with plants and flowers on Shavuot was recorded in a collection of festival customs from as long ago as the 12th century. The author of the book already then described the practice as an ancient tradition. It is not clear however exactly when the practice first started. The custom is quoted in the Code of Jewish Law chapter 494 paragraph 3.
There are two reasons given for the practice. The first being to commemorate the Giving of the Torah on Mount Sinai. The Talmud records that Mount Sinai and its environs were covered in lush vegetation and pretty flowers at the time of the Giving of the Torah, in stark contrast to the desert around it.
The second reason given is that Shavuot was the time when farmers would bring their gifts of the first fruit of the harvest to the Temple in Jerusalem.
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