From Sahih Muslim (Hadith 3459):
Abu Huraira (Allah be pleased with him) reported Allah's Messenger (ﷺ) as having said this:Do not outbid in a sale in order to ensnare. No man should enter into a transaction in which his brother has already entered, and no dweller of the town should sell on behalf of the villager. And no man should make a proposal of marriage which his brother has already made and no woman should ask for the divorce of another (co-wife) in order to deprive her of what belongs to her
Reference: Muslim 3459