Arabic (بيع الثنيا) for a sale (bay’) with exclusion. It is a type of sale in which an unknown part of the object of sale is excluded from the transaction. More specifically, the two parties to the contract could agree that a part of the goods, not exactly specified, will not be included in the sale.

For instance, a farmer could sell an amount of wheat for a specific price (thaman) except a part of it which might be eaten by fowls. The stipulation to exclude a uncertain amount of wheat leads to gharar (on the side of the buyer who doesn’t know the exact amount he will get in return for the price he paid). In this sense, bay’ al-thunya belongs to the class of bay’ al-gharar, and is, thus, impressible under shari’a.

Bay’ al-thunya may also refer to bay’ al-wafa (or bay’ al-uhdah, bay’ al-amanah, bay’ al-ta’ah, bay’ al-ja’iz) which translates as discharge sale or return sale. It is a sale and purchase between two parties at a specific price on the condition that whenever the seller pays back the purchase price, the buyer shall return the object of sale to him or vice versa.