وكذلك لو باع عبدا على أن يستخدمه البائع شهرا أو دارا على أن يسكنها أو على أن يقرضه المشتري درهما أو على أن يهدي له هدية
Translation: A sale is likewise defective if conditioned on a month of service to the seller, the seller’s continued residence in the sold house, or a loan or gift from the buyer.
Here the seller reserves an additional personal benefit beyond the sale itself.
Examples:
1. The seller makes one month of personal use of the sold house a condition of selling it.
2. The purchaser must also lend money or make a separate gift.
The rule depends on whether the added requirement is part of a lawful sale obligation, valid custom, or a prohibited benefit; do not class every ordinary commercial term identically.