Ibn 'Umar (RA) reported Allah's Apostle (ﷺ) as having said this: None amongst you should outbid another in a transaction, nor should he make proposals of marriage upon the proposal made by someone else.
Ibn 'Umar (RA) reported Allah's Apostle (ﷺ) as having said this: A person should not enter into a transaction when his brother (had already entered into but not finalised), and he should not make proposal of marriage upon the proposal already made by his brother, until he permits it.
Abu Hurairah (RA) reported Allah's Apostle (ﷺ) as having forbidden a dweller of the town selling the merchandise of a villager or outbidding in a sale (in order that another might fall into a snare), or a person making the proposal of marriage when his brother has already made such a proposal, or entering into a transaction when his brother has already entered; and a woman asking the divorce of her sister in order to deprive her of what belongs to her. 'Amr made this addition: "The person should not purchase in opposition to his brother."
Abu Hurairah (RA) 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.
Abu Hurairah (RA) reported Allah's Messenger (ﷺ) as saying: The Muslim should not purchase in opposition to his brother, and he should not make the proposal of marriage on the proposal already made by his brother.
'Uqba bin 'Amir said on the pulpit that Allah's Messenger (ﷺ) said: A believer is the brother of a believer, so it is not lawful for a believer to outbid his brother, and he should not propose an engagement when his brother has thus proposed until he gives it up.