Specific vs. Non-Specific Commodities
In Islamic Finance, the shari’ah differentiates between two types of commodities (this is just one differentiation): specific, and non-specific.
Specific: “I’ll sell you this Saheeh Bukhari printed in 2004 by Dar-us-Salaam that I’m holding in my hand.”
Non-Specific: “I’ll sell you a copy of Saheeh Bukhari printed in 2004 by Dar-us-Salam.”
So if you own some large amount of inventory, or you sell in volume, or you have a bookstore, etc.