What is the ruling on contracting with a craftsman (like a miller) to perform work in exchange for a known measure of the processed product (e.g., a *qafiz* of flour per measured *qafiz* milled)?

Primary text

The prohibition against the Miller's Qafiz (*Qafiz al-Tahan*), where known measures of grain are given to the miller to grind in exchange for a measure of the resulting flour, is based on making some of the processed product the wage for the work, effectively making the grinding due to the miller. However, this specific Hadith regarding the miller is not established or considered sound by this authority. The principle derived from Ahmad's other rulings suggests its permissibility due to similarity with *Musaqah* and *Muzara'ah*.