Sahih Muslim 3812
صحيح مسلم#3812SahihIbn '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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 21:12