Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "When you trade by 'inah (selling on credit and buying back for less), take hold of the tails of cattle, become content with farming and abandon jihad, Allah will impose upon you a humiliation which He will not remove until you return to your religion."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10703
Likewise (through another chain from Ata). It has also been narrated through two weak chains from Ata bin Abi Rabah from Ibn Umar.
It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) as mawquf (his own statement) that he disliked, and forbade, that a man should come and say: "Buy such-and-such, and I will buy it from you at such-and-such a profit."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10704
Sayyiduna Hakim bin Hizam (may Allah be pleased with him) said: I said to the Messenger of Allah (peace and blessings be upon him): O Messenger of Allah! A man comes to me (and asks): Sell me this thing; then should I go to the trouble of procuring it from the market for him? He (peace and blessings be upon him) said: "Do not sell what is not with you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10705