Do not mistreat your friend and you shall fear Hashem for I am Hashem your G-d.
Chazal tell us that this possuk teaches us not to tease another person, and not to say things that cause other people to be hurt.
However, the Ohr Hachaim writes that the simple meaning of the possuk is that it refers to the halacha of trickery in business. The previous prohibition (possuk 14) against trickery applies to the sale of portable items. As the possuk says וְכִי תִמְכְרוּ מִמְכָׁר לַעֲמִיתֶךָ אוֹ קָׁנֹה מִיַד עֲמִיתֶ ךָ אַל תוֹנוּ אִיש אֶת אָׁחִיו – when you shall sell something to your friend, or buy something from your friend, do not mistreat your brother. This applies only to things that can be passed from hand to hand, not real estate. The prohibition and rules of fraud in business pricing do not apply to real estate.
However, when learning this Halacha a person may mistakenly reach the conclusion that the matter is completely permitted, and the sale of real estate can be accompanied with fraudulent pricing practices. The Torah tells us, in this possuk, that even though a person is not obligated to return the money he has obtained through fraudulently inflating the price of the property, he would still be transgressing a Divine prohibition.
However, the Beis Din in this world does not adjudicate this kind of fraud. If a person overcharges or undercharges for real estate, there is no recourse in Beis Din. This is why the Torah continues with וְיָׁרֵׁאתָׁ מֵׁא לוֹקיךָ – and you shall fear Hashem. Only Hashem adjudicates this issue; the Beis Din will not enforce it. This does not detract from the severity of the prohibition.
The Torah then tells us the reason for this distinction. כִי אֲנִי ה' א לוֹקיכֶם – for I am Hashem your G-d. Hashem took this judgment for Himself. This is one of the Halachos that were passed to the Celestial Court.
The Ohr Hachaim explains the reason that this Halacha was left to the Celestial court. The price of real estate can never be absolutely quantified. There are no two properties that can be considered the same, because each is in its own location. The value the property provides to one person is not the same as the value it provides to another. The only way to evaluate a price is to compare the item with similar items and see how it sells in the marketplace. Seeing as no two pieces of real estate are truly similar, its evaluation can never be accurate.
When someone is overcharged for a piece of land, it is virtually impossible to research the true reason for the overprice. Was the seller tricking the buyer? Or was the property truly more valuable to him, for some reason? The only One who knows people’s thoughts is Hashem, and He is the only One who can decide whether the person has transgressed the prohibition or not. This is why this is in the hands of Hashem and Hashem only. On these occasions, the Torah adds the words אֲנִי ה' א לוֹקיכֶם – I am Hashem your G-d. I am Hashem that knows your true motivation, and I will judge you for this transgression.
