Once, in Israel, I had a conversation about politics with an Israeli I had recently met. Growing tired of the topic at hand, I decided to abruptly change the subject. My acquaintance was a little puzzled, expecting me to stick to the original subject. Immediately, without hesitation, this long-haired, secular teenager with cutoff jeans asked me, מה ענין שמיטה אצל הר סיני, “What does Shmittah have to do with Har Sinai?” This, as it turns out, is the standard Israeli way of asking what one topic has to do with another.
The question itself was first asked by Rashi. Parshat Behar opens with an unusual choice of words: וידבר ה' אל משה בהר סיני לאמר...כי תבואו אל הארץ אשר אני נותן לכם ושבתה הארץ שבת לה', “Hashem spoke to Moshe on Har Sinai saying…When you come to the land that I will give you, you should let it rest – a Shabbat for Hashem” (25:1-2).
An obvious question arises from the wording of these Pesukim. We know that the Mitzvot were all given at Har Sinai. Why must the Torah specifically mention that the Mitzva of Shmittah was given at Har Sinai?
Rashi teaches that this is in order to remind us that not only were the Mitzvot given at Har Sinai in the general sense, but their specific details were given as well.
The Sefat Emet offers another explanation. As human beings, it is easy to forget that while the laws of nature never change, it was Hashem who set them up in the first place (חוק נתן ולא יעבור). This, by definition, makes Hashem the true primary Force in the world. At Har Sinai, it was simply impossible not to recognize this; today, is it is a good deal more difficult. Shmittah, allowing the land to rest for a year, helps us to realize that it is, in fact, Hashem who controls the world.
The two ideas are not unrelated. The link is in the idea of Hashem being interested in details. Just as He did not just give a general framework without giving details for its use (i.e. תורה שבכתב and תורה שבעל פה), He did not set a wheel (i.e. the 'general' laws of nature) in motion and relinquish His own control over the details either. May we resist the temptation to forget that Hashem is interested in the details.