Narrated Abu Hurairah:The Messenger of Allah (ﷺ) as saying: Do not go out to meet riders to conduct business with them ; none of you must buy in opposition to one another; and do not tie up the udders of camels and sheep, for he who buys them after that has been done has two courses open to him after milking them: he may keep them if he is pleased with them, or he may return them along with a sa' of dates is he is displeased with them

English translation · Sunan Abu Dawud