"I asked Messenger of Allah ﷺ, I said: 'A man came to me asking to buy something that I did not have. Can I buy it from the market for him and then give it to him?' He said: 'Do not sell what is not with you.'" He said: There are narrations on this topic from 'Abdullah bin 'Umar.  

أَتَيْتُ رَسُولَ اللَّهِ ﷺ فَقُلْتُ يَأْتِينِي الرَّجُلُ يَسْأَلُنِي مِنَ الْبَيْعِ مَا لَيْسَ عِنْدِي أَبْتَاعُ لَهُ مِنَ السُّوقِ ثُمَّ أَبِيعُهُ قَالَ لاَ تَبِعْ مَا لَيْسَ عِنْدَكَ قَالَ وَفِي الْبَابِ عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ  

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

نَهَانِي رَسُولُ اللَّهِ ﷺ أَنْ أَبِيعَ مَا لَيْسَ عِنْدِي  

'Amr bin Shu'aib narrated to us, saying: My father narrated to me from his father' until he mentioned 'Abdullah bin 'Amr: "The Messenger of Allah ﷺ said: 'It is not lawful to lend and sell, nor two conditions in a sale, nor to profit from what is not possessed, nor to sell what one does not have.'"  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَحِلُّ سَلَفٌ وَبَيْعٌ وَلاَ شَرْطَانِ فِي بَيْعٍ وَلاَ رِبْحُ مَا لَمْ يُضْمَنْ وَلاَ بَيْعُ مَا لَيْسَ عِنْدَكَ  

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

نَهَانِي رَسُولُ اللَّهِ ﷺ أَنْ أَبِيعَ مَا لَيْسَ عِنْدِي