The validity of selling a portion of an item when only part of the whole has been received in a prior purchase.
Chapter on Selling Assets and Fruits
Al-Mughni
Book of Sales
Primary text
If a measure (Qafiz) of food is purchased, and only half of it is received, and then a man tells the purchaser to sell him half of this Qafiz, the sale is valid and pertains only to the half already received. This is because the sale is directed towards what the seller is legally permitted to sell, which is the portion already taken into possession.
Supporting text
If the man instead proposes partnership in the entire Qafiz for half the price, and the seller agrees, the partnership is invalid except for the portion already received. In the received half, it becomes a joint ownership where each party holds a quarter of the Qafiz according to their respective shares of the price. However, the correct view is that the partnership pertains to the entire half, following what is valid for sale and what is not, making it an instance of splitting the transaction (tafriq al-safqa), and thus invalid for the unreceived quarter. There are two differing opinions regarding the validity of the partnership for the received portion.