None amongst you should outbid another in a transaction, nor should he make proposals of marriage upon the proposal made by someone else.  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَبِعْ بَعْضُكُمْ عَلَى بَيْعِ بَعْضٍ وَلاَ يَخْطُبْ بَعْضُكُمْ عَلَى خِطْبَةِ بَعْضٍ  

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.  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَبِعِ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ إِلاَّ أَنْ يَأْذَنَ لَهُ  

The above hadith has been narrated by Ibn Umar through another chain.  

عَنْ عُبَيْدِ اللَّهِ بِهَذَا الإِسْنَادِ  

A hadith like this has been reported on the authority of Nafi' with the same chain of transmitters.  

عَنْ نَافِعٍ بِهَذَا الإِسْنَادِ  

" The person should not purchase in opposition to his brother."  

أَنَّ النَّبِيَّ ﷺ نَهَى أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ أَوْ يَتَنَاجَشُوا أَوْ يَخْطُبَ الرَّجُلُ عَلَى خِطْبَةِ أَخِيهِ أَوْ يَبِيعَ عَلَى بَيْعِ أَخِيهِ وَلاَ تَسْأَلِ الْمَرْأَةُ طَلاَقَ أُخْتِهَا لِتَكْتَفِئَ مَا فِي إِنَائِهَا أَوْ مَا فِي صَحْفَتِهَا زَادَ عَمْرٌو فِي رِوَايَتِهِ وَلاَ يَسُمِ الرَّجُلُ عَلَى سَوْمِ أَخِيهِ  

Do not outbid in a sale in order to ensnare. No man should enter into a transaction in which his brother has already entered, and no dweller of the town should sell on behalf of the villager. And no man should make a proposal of marriage which his brother has already made and no woman should ask for the divorce of another (co-wife) in order to deprive her of what belongs to her.  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ تَنَاجَشُوا وَلاَ يَبِعِ الْمَرْءُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَبِعْ حَاضِرٌ لِبَادٍ وَلاَ يَخْطُبِ الْمَرْءُ عَلَى خِطْبَةِ أَخِيهِ وَلاَ تَسْأَلِ الْمَرْأَةُ طَلاَقَ الأُخْرَى لِتَكْتَفِئَ مَا فِي إِنَائِهَا  

A hadith like this has been narrated on the authority of Zuhri with the same chain of transmitters but with a slight alteration.  

عَنِ الزُّهْرِيِّ بِهَذَا الإِسْنَادِ مِثْلَهُ غَيْرَ أَنَّ فِي حَدِيثِ مَعْمَرٍ وَلاَ يَزِدِ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ  

The Muslim should not purchase in opposition to his brother, and he should not make the proposal of marriage on the proposal already made by his brother.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَسُمِ الْمُسْلِمُ عَلَى سَوْمِ أَخِيهِ وَلاَ يَخْطُبْ عَلَى خِطْبَتِهِ  

This hadith has been narrated on the authority of Abu Huraira (Allah be pleased with him) through another chain of transmitters.  

عَنِ النَّبِيِّ ﷺ ح وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ الْمُثَنَّى حَدَّثَنَا عَبْدُ الصَّمَدِ حَدَّثَنَا شُعْبَةُ عَنِ الأَعْمَشِ عَنْ أَبِي صَالِحٍ عَنْ أَبِي هُرَيْرَةَ عَنِ النَّبِيِّ ﷺ إِلاَّ أَنَّهُمْ قَالُوا عَلَى سَوْمِ أَخِيهِ وَخِطْبَةِ أَخِيهِ  

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.  

أَنَّهُ سَمِعَ عُقْبَةَ بْنَ عَامِرٍ عَلَى الْمِنْبَرِ يَقُولُ إِنَّ رَسُولَ اللَّهِ ﷺ قَالَ الْمُؤْمِنُ أَخُو الْمُؤْمِنِ فَلاَ يَحِلُّ لِلْمُؤْمِنِ أَنْ يَبْتَاعَ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبَ عَلَى خِطْبَةِ أَخِيهِ حَتَّى يَذَرَ