Sahih Muslim

Abu Huraira (Allah be pleased with him) reported that Allah's Messenger (ﷺ) 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.