Ibn 'Umar (Allah be pleased with them) reported Allah's Messenger (ﷺ) as having said this
One amongst you should not enter into a transaction when another is bargaining.
Ibn 'Umar (Allah be pleased with them) reported Allah's Messenger (ﷺ) as saying
A person should not enter into a transaction when his brother is already making a transaction and he should not make a proposal of marriage when his brother has already made a proposal except when he gives permission.
Abu Huraira reported Allah's Messenger (ﷺ) as saying
A Muslim should not purchase (in opposition) to his brother.
This hadith has been narrated on the authority of Abu Huraira through another chain of transmitters but with a slight change of words.
Abu Huraira reported Allah's Messenger (may peace'be upon him) as saying
Do not go out to meet riders to enter into transaction with them; none of you must buy in opposition to another, nor must you bid against one another; a townsman must not sell for a man from the desert, and do not tie up udders of carnels and sheep, and he who buys them after that has been done has two courses open to him: after he has milked them he may keep them if he is pleased with them, or he may return them along with a sit of dates if he is displeased with them.
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.
This hadith has been narrated through another chain of transmitters.
Ibn Umar (Allah be pleased with them) reported that Allah's Messenger (ﷺ) forbade the outbidding (against another).