What is the ruling if an unknown reward (Thawab ma'hool) is stipulated in a gift?
General Chapter
Al-Mughni
Book of Gifts and Donations
Primary text
If an unknown reward is stipulated, the gift contract is void, and the contract is ruled as a corrupted sale (Bay' Fasid). The recipient must return the gifted item along with any attached or separated increase, as this increase is considered growth of the donor's property. If the item has been destroyed, its value must be returned. This is the view of Al-Shafi'i and Abu Thawr.
Supporting text
The apparent view of Ahmad suggests the contract may be valid initially. If the donor later provides a recompense that the recipient accepts, the contract is finalized by that acceptance, treating it as a sale by mutual exchange (Bay' bi al-Mu'atah) established by mutual consent.