Unity binds shmittah and ona'ah

ענין סמיכת פ' אונאה לשמיטה.

The matter of why the parsha of ona'ah (wronging another in business) is placed adjacent to shmittah.

The Sefas Emes opens by asking why the Torah juxtaposes the prohibition of overcharging or deceiving in commerce with the laws of the sabbatical year.

הגם דכ' מעט השנים תמעיט כו' עכ"ז עיקר אונאה אינו דוקא בענין שמיטין.

Even though it is written, "according to the fewness of the years you shall lower its price," etc. — nevertheless, the essence of ona'ah is not specifically about the shmittah years.

One might think the connection is merely practical, since the price of a field depends on how many years remain until shmittah. But the Sefas Emes says the real bond between them runs deeper than pricing.

אבל באמת עיקר אל תונו הוא כדי להיות בנ"י באחדות כמ"ש חז"ל שאונאת דברים ג"כ בכלל.

But in truth the essence of "do not wrong one another" is so that Bnei Yisrael should be in achdus (unity), as Chazal said that ona'as devarim (wronging with words) is also included.

Since the prohibition extends even to causing pain with mere words, its purpose cannot be only fair commerce — it is to bind Bnei Yisrael together in unity.

והנה מצות השמיטה אינה מצוה פרטית אבל כפי האחדות שיש בבנ"י יכולין לקיים זאת המצוה.

Now, the mitzvah of shmittah is not a private mitzvah; rather, in accordance with the unity that exists among Bnei Yisrael, they are able to fulfill this mitzvah.

Shmittah is a collective mitzvah of the entire nation, and the strength to keep it flows precisely from the achdus of Klal Yisrael.

כמ"ש בזמן שכל יושבי' עלי' כו'.

As it is written, "when all its inhabitants are upon it," etc.

The full obligation of shmittah and yovel applies only when all of Bnei Yisrael are settled together in the Land — again pointing to unity as its precondition.

וכמו בשבת מתיחדין בו ברזא דאחד ע"י השבת.

And just as on Shabbos they become unified through the secret of "One" by means of Shabbos.

Shabbos itself draws all the souls of Bnei Yisrael into the mystery of oneness, binding them to the One Above.

ושמיטה תלוי' בבנ"י ובקידוש ב"ד.

And shmittah depends upon Bnei Yisrael and upon the sanctification of beis din (the court).

Unlike Shabbos, the shmittah cycle is established by the human court's counting and sanctifying of the years — so it rests on the action of the nation.

לכן ע"י האחדות באין לשביתת שמיטה.

Therefore, it is through unity that one arrives at the rest of shmittah.

Because shmittah hangs on the people themselves, only their achdus enables them to reach its sanctity and rest.

אבל שבת קבוע וקיימא מביא האחדות מעצמו.

But Shabbos, which is fixed and standing, brings the unity by itself.

Shabbos is set in the order of creation and does not depend on us; it generates unity on its own, whereas shmittah requires us to generate it first.

ולכן חרב המקדש ע"י שנאת חנם וע"י ביטול שמיטין ויובלות כי הכל ענין אחד כנ"ל:

And therefore the Mikdash was destroyed through baseless hatred and through the neglect of shmittos and yovlos, for it is all one matter, as above.

Sinas chinam and the abandonment of shmittah are two faces of the same failure — the breakdown of unity — and that single flaw brought the churban of the Bais Hamikdash.

Summary: Ona'ah and shmittah are placed together because both exist to forge the achdus of Bnei Yisrael. Shabbos creates unity on its own, but shmittah depends on the nation's own unity to be fulfilled; the loss of that unity — through baseless hatred and the neglect of the sabbatical years — is what brought about the destruction of the Bais Hamikdash.