Sahih Muslim 3455
صحيح مسلم#3455SahihIbn Umar (Allah be pleased with them) 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
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: 16:58