عَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ لَا يَبِيعْ أَحَدُكُمْ عَلَى بَيْعِ أَخِيهِ وَلَا يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ إِلَّا أَنْ يَأْذَنَ لَهُ
Narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Noble Prophet (peace and blessings be upon him) said: No man should sell over his brother’s sale, nor should he propose over his brother’s proposal, unless he gives him permission.