ونهى رسول الله صلى الله عليه وسلم عن النجش وعن السوم على سوم غيره وعن تلقي الجلب وعن بيع الحاضر للبادي وعن البيع عند أذان الجمعة وكل ذلك يكره ولا يفسد به العقد
Translation: The Prophet forbade fraudulent bidding, intervening in another’s bargain, intercepting incoming traders, the described town-dweller/outsider arrangement, and selling at the Friday call to prayer; Quduri states that these are objectionable yet do not by themselves invalidate the contract.
Najsh is artificial bidding without an intention to buy. Sawm ‘ala sawm al-ghayr interferes with an existing bargain. Talaqqi al-jalab involves intercepting incoming traders before market access in prohibited circumstances.
Quduri distinguishes objectionable conduct from the technical validity of the sale. Not voiding the contract does not make the conduct permissible.