حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ نُمَيْرٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ لاَ يَخْطُبُ أَحَدُكُمْ عَلَى خِطْبَةِ أَخِيهِ وَلاَ يَبِيعُ عَلَى بَيْعِ أَخِيهِ إِلاَّ بِإِذْنِهِ ‏"‏ ‏.‏

Narrated Abdullah ibn Umar: The Prophet (PBUH) said: One of you must not ask a woman in marriage when his brother has done so already, and one of you must not sell (his own goods) when his brother has already sold (his goods) except with his permission. Translation Not Available

Book Ref: Sunan Abi Dawud Book 12 Hadith 2081
Web Ref:  Sunan Abi Dawud Book 11 Hadith 2076