Narrated Abu Hurairah:
The Messenger of Allah ﷺ as saying: Do not go out to meet riders to conduct business with them ; none of you must buy in opposition to one another; and do not tie up the udders of camels and sheep, for he who buys them after that has been done has two courses open to him after milking them: he may keep them if he is pleased with them, or he may return them along with a sa' of dates is he is displeased with them.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " لاَ تَلَقَّوُا الرُّكْبَانَ لِلْبَيْعِ وَلاَ يَبِعْ بَعْضُكُمْ عَلَى بَيْعِ بَعْضٍ وَلاَ تُصَرُّوا الإِبِلَ وَالْغَنَمَ فَمَنِ ابْتَاعَهَا بَعْدَ ذَلِكَ فَهُوَ بِخَيْرِ النَّظَرَيْنِ بَعْدَ أَنْ يَحْلِبَهَا فَإِنْ رَضِيَهَا أَمْسَكَهَا وَإِنْ سَخِطَهَا رَدَّهَا وَصَاعًا مِنْ تَمْرٍ " .