Sahih Muslim
The Book of Transactions (Kitab Al-Buyu)
Book Number: 010 / Hadith Number: 3621
Abu Huraira (Allah be pleased with him) reported that Allah's Messenger (may peace be upon him) forbade the (people) meeting the caravan (for entering into business transaction with them), and the selling of goods by a townsman on behalf of a man of the desert, and seeking by a woman the divorce of her sister (from her husband), and outbidding (against one another), and tying up the udders (of animals), and buying of (things) in opposition to one's brother. This hadith has been narrated through another chain of transmitters.