Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Do not inflate prices, no town-dweller should sell for a desert-dweller, no man should strike a deal over another's deal, and he should not send a proposal over his brother's marriage proposal."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10900
Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Do not go out to meet the trade caravans outside the town; no one should strike a deal over another's deal; do not (deceptively) inflate prices; no town-dweller should sell for a desert-dweller; and do not sell camels and goats with milk withheld in their udders. If anyone buys such an animal (whose milk has not been drawn for several milkings), then after milking it he may choose whichever of the two options he wishes: if he is pleased with the animal he keeps it; otherwise he returns the animal along with a sa' of dates."
(b) Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) forbade "that a Muhajir should sell for a Bedouin."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10901
Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said: "No town-dweller should sell for a desert-dweller." The narrator says: I said: (What is meant by) a town-dweller should not sell for a desert-dweller? He said: It means that he should not become his broker.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10902
Sayyiduna Anas (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "No town-dweller should become the broker of a desert-dweller, even if he is his brother or his father."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10904
It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "No town-dweller should become the broker of a desert-dweller. Leave people to their affairs; some of them are given provision through others."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10905
Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said: "No town-dweller should sell for a desert-dweller."
This hadith with this chain is counted among the narrations that al-Shafi'i alone reported from Malik.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10906
Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said: "No town-dweller should sell for a desert-dweller."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10907
Abdullah bin Maslamah al-Qa'nabi mentioned something similar (through another chain).
It has also been narrated by Abd al-Rahman bin Abdullah bin Dinar, from his father, from Ibn Umar. Malik bin Anas has musnad narrations that he did not include in the Muwatta'; the senior ones among his companions narrated them from him outside the Muwatta'. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10908