Mukhtasar Bukhari (Abridged) 1020 — Do not sell over your brother's

Narrated Abu Huraira (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) forbade that any townsman should sell the goods of a desert-dweller (outsider), and that the seller should not be told a higher price than the buyer’s price so that he may not sell, while the one telling does not intend to buy himself. And no person should sell over the sale of his brother, nor should he send a marriage proposal to a woman after his brother has already proposed to her, and no woman should seek to have her (Muslim) co-wife divorced with the intention that what is in her co-wife’s mouth may come into her own mouth.