Sahih Muslim 1412
صحيح مسلم#1412Sahihحَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، وَمُحَمَّدُ بْنُ الْمُثَنَّى، - وَاللَّفْظُ لِزُهَيْرٍ - قَالاَ حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، أَخْبَرَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " لاَ يَبِعِ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ إِلاَّ أَنْ يَأْذَنَ لَهُ " .
Ibn '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
The label above is the grade most of these scholars gave, each scholar counted once — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. When they judged only its chain of narrators (“Isnaad”), the label says “Sound chain”. Each scholar's own wording:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
Sahih Muslim 1412 is the standard (Abd al-Baqi) number; this narration is #3812 in the MuslimGPT index.
In-book reference: 21:12