A form of prohibited sale (bay’ batil) in which a person or group of persons connive with a seller to bid up the price of a commodity offered for sale through an auction (mazad), not meaning to purchase but only to entice an unsuspecting bidder to offer higher prices, and eventually have him stuck with the object of sale. The ensnared buyer will have to pay an artificially determined price (a much higher price than fair or normal price). Bay’ al-najsh is an Arabic term that translates into sale by a fraudulent auction or sale by a manipulative overpricing. This sale is based on collusion (tawatu’) between a seller and a fake bidder.

Najsh (often misspelled as najash) literally means concealment, rousing and chasing the game for the purpose of entrapping it.

Bay’ al-najsh (in Arabic script بيع النجش) is also known as bay’ al-tanajsh.