Is the sale of a house excluding a specific measurement valid?
Chapter on Selling Assets and Fruits
Al-Mughni
Book of Sales
Primary text
The sale of a house excluding a specific unit of measurement, such as an arm's length (dhira'), is valid if both the seller and buyer know the actual dimensions of the house. This is permissible because the exclusion constitutes a specified, divisible portion of the whole, which could validly be sold independently, similar to excluding a third or a quarter of the property. Since the excluded portion is a known quantity being excepted from a known sold item (known by visual inspection), the transaction is upheld.
Supporting text
If the actual dimensions of the house are unknown to the parties, the sale is invalid because the excluded portion becomes an indeterminate unknown quantity that cannot legally be excluded from a sale. This is analogous to excluding a measure (sa' or qafiz) from a known quantity of harvested fruit (thamar al-ha'it or sabra), which invalidates the transaction when the actual total quantity is unknown.