[Machine] The Messenger of Allah ﷺ forbade selling a sale that has already been made and he used to say, "Do not overbid in transactions and do not sell what has already been bought, and do not propose to a woman who is already engaged to her brother until he leaves or gives permission to propose."
نَهَى رَسُولُ اللهِ ﷺ أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ وَكَانَ يَقُولُ لَا تَلَقَّوْا الْبُيُوعَ وَلَا يَبِعْ بَعْضٌ عَلَى بَيْعِ بَعْضٍ وَلَا يَخْطُبْ أَحَدُكُمْ أَوْ أَحَدٌ عَلَى خِطْبَةِ أَخِيهِ حَتَّى يَتْرُكَ الْخَاطِبُ الْأَوَّلُ أَوْ يَأْذَنَ لَهُ فَيَخْطُبَ