People came to Hakîm ibn Hizâm (may Allah be pleased with him) to buy goods.
Sometimes a man asked him for something he did not have.
He could buy it at the market and pass it on. Before doing so, he went to ask the Prophet ﷺ.
The answer fits in five words: “Do not sell what is not with you.”
“With you” means what you own and can hand over, not what you hope to find later.
Why such a firm answer? The jurists look at what can go wrong between the sale and the delivery.
The price may rise. The item may run out. Meanwhile, the buyer has paid for a promise.
Another hadith gives a clue: no profit on what you do not bear the risk of.
O you who believe, do not consume one another's wealth unjustly,
but only in trade by mutual consent among you.
A buyer who receives nothing, or something else, never consented to that.
Hakîm also narrated: if buyer and seller speak the truth and make things clear, their sale is blessed.
If they hide and lie, the blessing of their sale is wiped out.
Selling what you do not have, then hoping it works out, is the opposite of making things clear.
A customer wants an item you do not have. You could buy it afterwards and keep the difference.
Is that a sale? A Companion once asked the Prophet ﷺ this very question.
Hakîm had a doubt about his trade, and he took it straight to the Prophet ﷺ before acting.
Tonight, list what you sell or promise, and mark anything you could not hand over tomorrow.