بَابُ الْبَيْعِ الْفَاسِدِ
إذا كان أحد العوضين أو كلاهما محرما فالبيع فاسد كالبيع بالميتة أو بالدم أو بالخمر أو بالخنزير وكذلك إذا كان غير مملوك كالحر وبيع أم الولد والمدبر والمكاتب فاسد
Translation: A sale is defective or invalid when one or both countervalues are prohibited, such as carrion, blood, wine or swine, or when the purported subject is not validly owned, such as a free person or the historically listed classes of enslaved persons.
Countervalues (al-‘iwadayn) are the goods and their consideration. The subject of exchange must count as legally recognized property.
Fath al-Qadir explains the technical qualification behind Quduri's broader wording: carrion, blood and a free person can render the transaction void, while wine or swine used as price raise a separate defective-sale classification. These examples cannot all be treated identically.
The references to enslavement describe historical juristic institutions and are not contemporary commercial permissions.