What are the connotations of the double Lashon "Even Sheleimah va'Tzedek"?
Targum Yonasan: "Even Sheleimah" refers to weights and "va'Tzedek" to scales; "Eifah Sheleimah" refers to dry measures and "va'Tzedek", to (weighing) jugs.
Bava Basra, 88b: We Darshen from "va'Tzedek" 'Tzadek mi'shel'cha ve'Ten lo!' - When the scales are exactly correct, one should tip them a little in favor of the purchaser. 1
Bava Basra, 89b: To prohibit the shopkeeper from selling the exact amount where the Minhag is to add a litle extra and the purchaser from adding a little extra where the Minhag is to weigh out the exact amount - even with the consent of both parties. 2
What are the connotations of the double Lashon "Eifah Sheleimah va'Tzedek Yih'yeh lach"?
Bava Basra, 89b: To prohibit the shopkeeper from flattening the pile where the Minhag is to add to it and the purchaser from adding to the pile where the Minhag is to flatten it 1 - and even if the shopkeeper is willing to deduct accordingly from the price and the purchaser is willing to pay more.
Why does the Torah repeat the words "Yih'yeh lach"?
Rashi: To teach us that conversely, 1 if you possess only correct weights and measures, you will have a lot.
Sifri: The Chachamim learn from here that the merchant should clean his measures once every thirty days and the Balabos, once every twelve months.
See Sifsei Chachamim.
What are the implication of "Lema'an Ya'arichu Yamecha .. "?