Sahih Muslim 1516
Sahih Muslim · Book 21: The Book of Transactions · 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
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى ، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ ، عَنِ ابْنِ عُمَرَ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنِ النَّجْشِ .
Ibn Umar (Allah be pleased with them) reported that Allah's Messenger (ﷺ) forbade the outbidding (against another).