Narrated 'Abdullah bin 'Umar:

Allah's Apostle ﷺ said, "Do not urge somebody to return what he has already bought (i.e. in optional sale) from another seller so as to sell him your own goods."

حَدَّثَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ـ رضى الله عنهما ـ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ
" لاَ يَبِيعُ بَعْضُكُمْ عَلَى بَيْعِ أَخِيهِ ".