Is a sale valid if the price is contingent on an excluded portion of the sold item?
Chapter on Selling Assets and Fruits
Al-Mughni
Book of Sales
Primary text
The sale is valid if one states, "I sold you these fruits for four dirhams, except for an amount equal to one dirham." This is permissible because the excluded portion is determinable from the sold item, representing one-fourth, making the contract equivalent to selling three-fourths of the fruits for four dirhams.
Supporting text
The sale is invalid if one states, "except for what is equivalent to one dirham." This is invalid because the amount equivalent to one dirham could be one-fourth, or more or less, introducing uncertainty and thus invalidating the contract.