BAI’U ‘L-WAFA بيع الوفاء.
The word wafa means the performance of a promise, and the Bai’u l’ Wafa is a sale with a promise to be performed. It is, in fact, a pledge in the hand of the pawnee, who is not its propritor, nor is he free to make use of it without the permission of the owner. There are different opinions about the legality of this form of sale, but it is now the common form of mortgage in use in India, where it is usually styled Bai’ bi-’l-wafa. (See Baillie’s Muslim Law of Sale, p 303.)
Based on Hughes, Dictionary of Islam