The Book of Transactions
21/4. Chapter:
The prohibition of urging a buyer to cancel a purchase in order to sell him one's own goods; And urging a seller to cancel a sale already agreed upon so that one can buy the goods oneself; And the prohibition of artificially inflating prices; And the prohibition of letting milk accumulate in the udder in order to deceive the purchaser
Sahih Muslim
حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ، وَقُتَيْبَةُ بْنُ سَعِيدٍ، وَابْنُ، حُجْرٍ قَالُوا حَدَّثَنَا إِسْمَاعِيلُ، - وَهُوَ ابْنُ جَعْفَرٍ - عَنِ الْعَلاَءِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " لاَ يَسُمِ الْمُسْلِمُ عَلَى سَوْمِ أَخِيهِ " .
Abu Huraira reported Allah's Messenger (ﷺ) as saying: A Muslim should not purchase (in opposition) to his brother.
Reference : Sahih Muslim 1515aIn-book reference : Book 21, Hadith 13USC-MSA web (English) reference : Book 10, Hadith 3619