حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ الْقَعْنَبِيُّ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يَبِعْ بَعْضُكُمْ عَلَى بَيْعِ بَعْضٍ وَلاَ تَلَقَّوُا السِّلَعَ حَتَّى يُهْبَطَ بِهَا الأَسْوَاقَ ‏"‏ ‏.‏

Narrated 'Abdullah bin 'Umar: The Messenger of Allah (PBUH) as saying: None of you must buy in opposition to one another ; and do not go out to meet the merchandise, (but one must wait) till it is brought down to the market. Translation Not Available

Book Ref: Sunan Abi Dawud Book 24 Hadith 3436
Web Ref:  Sunan Abi Dawud Book 23 Hadith 3429