One amongst you should not enter into a transaction when another is bargaining.
Sahih Muslim Book 21, Hadith 11
← Previous Hadith Ibn 'Umar (Allah be pleased with them) reported that the people of pre-Islamic days used to sell the meat of the slaughtered camel up to habal al-habala. And habal al-habala implies that a she-camel should give birth and then the (born one should grow young) and become pregnant. Allah's Messenger (ﷺ) forbade them that (this transaction).

Sahih Muslim Book 21, Hadith 10 Next Hadith → 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.

Sahih Muslim Book 21, Hadith 12