Narrated Hakim b. Hizam:

"The Messenger of Allah (ﷺ) prohibited me from selling what was not with me."

[Abu 'Eisa said:] This Hadith is Hasan. He said: There is something on this topic from 'Abdullah bin 'Umar.

Ishaq bin Mansur said: "I said to Ahmad: 'What is the meaning of the prohibition from a loan along with a sale? He said: 'That he gives him a loan and then he makes a sale to him greater then it's actual worth. And, it carries the meaning of him loaning it to him in exchange for something (as collateral), so he says: 'If you are unable to pay it (the loan), the it (the collateral) will be a sale for you.' Ishaq [bin Rahuwyah] said as he said. And I said to Ahmad: 'What about selling what one does not possess?' He said: 'To me it does not apply except in cases of food - meaning one has not taken possession of it.' And Ishaq said the same for all of what is measured or weighed. Ahmad said: 'When he says: "I will sell you this garment, with the condition that I am the tailor for it, and I am the one who bleaches it.' This is an example of two conditions in one sale. But if he says: "I am selling it to you with the condition that I am its tailor," then there is no harm in it. And, if he said: "I am selling it to you with the condition that I am the one who bleaches it" then there is no harm in it, because this is only one condition.' And Ishaq said as he said."