Arabic (البيع على البيع) for sale (bay) over another sale (bay) transaction. It involves an attempt by a third party (a new seller), during the period of khiyar (zaman al-khiyar– the typical three-day grace period), to sell his commodity while the sale transaction is being negotiated and is about to conclude between two parties. To that end, the new seller may quote a lower price or draw attention to defects/ imperfections in the commodities being sold by the other seller. By so doing, the new seller disturbs the transaction and tries to take the place of the original seller.

This sale (bay’) belongs to the class of prohibited sales under shari’ah.