Sahih Muslim 3464
صحيح مسلم#3464SahihUqba b. '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
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: 16:66