Parashas Behar · Aliyah 2 · Passuk 25:14
Chabad.org — English translation + Rashi
Torah Temimah cites Sifra (Torat Kohanim) Behar, Section 3.
English: “And when you sell a sale to your fellow.” From where do we know that when you sell, sell to your fellow Yisrael? The verse says “and when you sell a sale to your fellow — sell.” And from where that if you come to buy, buy from your fellow Yisrael? The verse says “or buy from the hand of your fellow.”
Classical derasha (Sifra).
When selling or buying, preference is given to a fellow Jew.