וְכִי תֹאמְרוּ, מַה-נֹּאכַל בַּשָּׁנָה הַשְּׁבִיעִת: הֵן לֹא נִזְרָע, וְלֹא
וְצִוִּיתִי אֶת-בִּרְכָתִי לָכֶם, בַּשָּׁנָה הַשִּׁשִּׁית; וְעָשָׂת, אֶת-הַתְּבוּאָה, לִשְׁלֹשׁ, הַשָּׁנִים.
My grandfather asks why was that not placed next to the earlier mention? Why the disruption of the flow from one point on shmitta to this one with the point about not cheating or misleading someone when making a sale of property?
He suggests that the question ?מַה-נֹּאכַל is the motivation behind the attempt to cheat others. It is only made explicit in the context of shmitta because there it is spoken overtly. When it comes to seeking to get the better of someone else in a business deal, though, the same concern drives the action. The difference is that with respect to beyn adam lechavero, the person usually does not articulate it and may not even be conscious of it.
In fact, though, the blessing Hashem extends to people who act with faith with respect to shmitta also extends to acting in good faith in business. In my grandfathers's word, "Aval be'emeth al ha'adam lada'as shebirchath Hashem ta'ashir gam beyachso livney adam im rap ya'ase hayahar vehatov."
And the entire parsha's intent is to teach us middat habritachon behashgachas Hasehm.
Related post: http://kallahmagazine.blogspot.com/2015/10/dvar-yehudah-parsha-points-from-my.html