Why does the Torah add the word "la'Amisecha" both in connection with selling and in connection with purchasing?
Rashi: This is the way the Torah speaks.
Rashi (from Toras Kohanim): To teach us that wherever possible, one should purchase from one's fellow-Jew.
Bechoros 13a-b: A Nochri acquires [Metaltelim] unlike your fellow Jew. A Jew acquires via Meshichah, and a Nochri via Kesef, or the reverse, according to R. Yochanan (mid'Oraisa).
Refer to 25:14:152:1.
Why does the Torah insert the word "mi'Yad"?
Ramban #1 (citing Bava Metzi'a, 56b): to confine the Isur Ona'ah to Metaltelin
Why does the Torah write twice the Lav of Ona'ah (here and in Pasuk 17)?
Rashi: Ona'ah in this Pasuk refers to Ona'as Mamon (overcharging or underpaying), whereas in Pasuk 17 it refers to Ona'as Devarim (aggrieving verbally). 1
Seforno (17): Pasuk 17 refers to Ona'as Mamon and Ona'as Devarim.
What are the ramifications of "Lo Sonu"?
Ramban #2: It is a warning that the two parties should clarify to one another how many years there are until the Yovel, and to stipulate that, in the Yovel, the field must go back to the seller.
Seforno: "v'Chi Simk'ru Mimkar ... " refers to the seller cheating - such as by removing the chaff from the top of the pile but not from the bottom; 1 whereas "Oh Kanoh ... "refers to the buyer underpaying, i.e. when the seller does not know the market price. 2
What is considered Ona'ah? What happens if somebody transgresses?
Ramban: For Metaltelim, if the difference from the true value is less than a sixth, the sale remains intact and the transgressor is not obligated to compensate the other party. 1 If it is a sixth 2 , the sale is valid, but the transgressor must return it. If it is more than a sixth, the sale is invalid.
Ramban: Such a small amount is pardoned. Nevertheless, the transgressor has contravened the Lav of Lo Sonu.
Riva, Moshav Zekenim (17, citing R. Yehudah ha'Chasid): A hint to this is the final letters of "[v'Lo Sonu] Ish Es Achiv v'Yaresa" (verse 17), which spell 'Shtus' (a sixth, in Arameic. Perhaps they hold like Seforno, that verse 17 applies also to Ona'as Mamon.
What is the reason for the sequence of all the current Parshiyos?
Rashi (26:1): First the Torah warns about Shemitah (and Yovel); in the event that someone has a lust for money and is suspect on Shemitah, he will be forced to sell his Metaltelin (movable goods [Pasuk 14), then, his fields (Pasuk 15), then his house (Pasuk 29); If he continues to transgress, he will be forced to borrow on interest (Pasuk 35); and finally, to sell himself, first to a Yisrael (Pasuk 39), and then, to a Nochri (Pasuk 47). 1
Rashi: Each punishment is worse than the one that precedes it.
Why does it say "Simkeru Memkar
Moshav Zekenim: We read these like 'Mem (40) Kor' and 'Oh Kaneh', to forbid Ona'ah both for a giant field (3,000,000 square Amos) and a tiny field (the size of one stick).
Ramban, Moshav Zekenim (15): The Torah initially taught the plural "Simkeru" to include land and Metaltelim, and switched to the singular "Kano" to hint that Metaltelim are different (sometimes there is compensation, or the sale is Batel).
Moshav Zekenim, Ibn Ezra: The plural "Simkeru" teaches to sell [land] in front of witnesses. "Kano" warns a buyer [not to underpay],
What do we learn from "Es Achiv"?
Moshav Zekenim #1: Do not say that Ona'ah applies only to an Ish; "Es Achiv" is extra to include women.
Moshav Zekenim #2: Do not say that Ona'ah applies only between merchants; "Es Achiv" includes even if one or both parties are commoners.
Bechoros 13b: From "la'Amisecha" and "Achiv" we exclude Nochrim and Hekdesh. 1
Moshav Zekenim #3: It excludes a minor who overcharged or underpaid an adult.
Moshav Zekenim: "Achiv" excludes Nochrim.