'Sell not what is not with you' means not to sell what you do not own (ya'ni ma laysa fi milkik) at the time of sale. One of the basic requirements of sale, as al-Kasani has stated, is that the seller owns the object of sale when he sells it, failing which the sale is not concluded, even if the seller acquires ownership afterwards. The only exception, in this context, is the forward sale of salam, where ownership is not a prerequisite. This is confirmed, al-Kasani adds, by the text of the hadith in which Hakim ibn Hizam reported that he would sell what he did not have, which means that which he did not own. He would take the price of the object from the prospective buyer, buy the goods in the market and then deliver them but, when the Prophet learned of this, he discouraged it. When Hakim ibn Hizam sold the goods to his customers, he attempted to transfer the ownership of those goods at the time when he received the price, which was unfeasible, since he could not transfer the ownership of what he himself was not the owner of. Al-San'ani has concurred with this interpretation and stated that 'sell not what is not with you' implies that it is not permissible to sell something before owning it. Ibn al-Humam and Ibn Qudamah have similarly concluded that the sale of something which the seller does not own is not permissible, even if he buys and delivers it afterwards.

The Hanafis have elaborated, however, that the seller's ownership of the object of sale is not a condition of the validity (shart al-sihhah), but of the effectiveness (nifadh) of the sale. Thus they validate the bona fide sale by an unauthorised person (al-fuduli) who does not own the object but nevertheless sells it (for a good reason), because in this case the sale is valid but not effective, and it becomes effective upon obtaining the consent of the owner.