I came to the Messenger of Allah ﷺ and said, "A man comes to me asking to buy something I do not have. Should I purchase it from the market and then sell it to him?"He said, "Do not sell what you do not possess."
حدثنا قتيبة حدثنا هشيم عن أبي بشر عن يوسف بن ماهك
أتيت رسول الله ﷺ فقلت يأتيني الرجل يسألني من البيع ما ليس عندي أبتاع له من السوق ثم أبيعه قال لا تبع ما ليس عندك
Selling what is not in one's possessionTakhrij, its isnad is hasan. Nasai narrated it, 7/289, no. 4617 (Chapter on Sales, section on the seller), from the hadith of Hushaym. Abu Dawud narrated it, no. 3503, and Ibn Majah, no. 2187, from the hadith of Abu Bishr with the same wording, and Ibn Hazm graded it sahih. It has many other chains found in Ibn Jarud, no. 602, and elsewhere.