688 – Abu Hurayrah (may Allah be pleased with him) reported: “The Messenger of Allah (peace and blessings be upon him) forbade a townsman to sell on behalf of a desert-dweller, to engage in najsh (bidding up the price without intending to buy), for one man to sell over his brother’s sale, to propose marriage over his brother’s proposal, and for a woman to ask that her sister be divorced so that she may overturn what is in her sister’s vessel.” Agreed upon.

Muslim also related: “A Muslim must not bid against the bidding of another Muslim.” ⦗1⦘

Lexical notes
• “He must not sell…”: the verb appears either in the indicative when lā is taken as a negating particle, or in the jussive when it is taken as a prohibitive particle.
• “Proposal (khiṭbah)”: the request for marriage, made to the woman herself or to her guardian.
• “So that she may overturn”: from kafaʾa al-ināʾ, meaning to tip a vessel over and empty its contents.
• “Bidding (sawm)”: from sāma – yasūmu; to offer a commodity and state its price.

Points derived from the ḥadīth
This report contains six prohibited matters:

1. “That a townsman sell on behalf of a desert-dweller,” and, “Do not engage in najsh”—both have been discussed previously.
2. The third: “A man must not sell over his brother’s sale.” That is, he says to someone who has purchased an item for ten: “I will give you the same item for nine,” or, “I will give you a better one for the same price,” seeking thereby to have him annul the sale and contract with him instead.
   The same ruling applies to buying over another’s purchase; for example, saying to someone who has sold an article for nine: “I will buy it from you for ten.” This falls under the same prohibition, for “sale” here embraces both selling and buying.