"I said: 'O Messenger of Allah, a man is asking me to sell him something that I do not possess; Shall I sell it to him?' He said: 'Do not sell what is not with you."' (Using translation from Ibn Mājah 2187)
قُلْتُ يَا رَسُولَ اللهِ الرَّجُلُ يَطْلُبُ مِنِّي الْبَيْعَ وَلَيْسَ عِنْدِي أَفَأَبْتَاعُهُ؟ فَقَالَ رَسُولُ اللهِ ﷺ «لَا تَبِعْ مَا لَيْسَ عِنْدَكَ»