TT #777 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:15
A complete and just weight you shall have, a complete and just measure you shall have, that your days may be prolonged in the land that the Eternal your God is giving you.
Torah Temimah points to Sifrei / Bava Batra.
TT lemma: אֶבֶן שְׁלֵמָה וָצֶדֶק.
אֶבֶן שְׁלֵמָה וָצֶדֶק יִהְיֶה לָּךְ – צֶדֶק מִשֶּׁלְּךָ וּצְדָקָה מִשֶּׁלּוֹ.
English: “A complete and just weight you shall have” — justice from yours and charity from his.
On the daf / in context: Some read the doubled language as requiring both strict justice and a measure of generosity toward the buyer.
Derash on the dual demand of justice and generosity.
Honest weights are required; some authorities also see a call for a slight generosity toward the purchaser.