A number of special laws and restrictions apply to produce grown in Israel during the Shemita year the seventh year in which agricultural activity is forbidden in Israel. Therefore, when one purchases Arba Minim (the four species) in preparation for Sukkot immediately after a Shemita year, certain precautions must be taken. These precautions apply only to the Etrog, which is an edible fruit; there are no restrictions concerning the purchase and use of Lulabim, Hadasim and Arabot grown in Israel during the Shemita year.
One simple way to avoid Shemita-related concerns is to purchase Moroccan Etrogim, or Etrogim grown anywhere outside Israel. If, however, one wishes to purchase an Etrog imported from Israel, he must ensure that the Etrog was grown and exported under the auspices of "Osar Bet Din." A full explanation of this procedure lies beyond the scope of our discussion, but briefly, "Osar Bet Din" means that a qualified Rabbinical court supervised the handling of the land and the produce during Shemita, to ensure that it was done in strict accordance with Halacha. After a Shemita year, it does not suffice for an Etrog to have authorization that it was not the product of grafting; it must also have been grown and exported under the auspices of the "Osar Bet Din" system. It should be noted that according to some authorities, using Etrogim from "Osar Bet Din" actually constitutes a special Misva. Not only are these Etrogim permissible for use on Sukkot, but they might also raise ones performance of this Misva to a higher standard.
Summary: If one purchases an Etrog imported from Israel immediately after a Shemita year, he must ensure that it was brought from Israel under the auspices of "Osar Bet Din." According to some authorities, there is a special Misva to use these Etrogim, rather than using Etrogim grown outside Israel.
