قَالَ مَالِكٌ عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنِ النَّجْشِ ‏.‏

Malik said, from Nafi from Abdullah ibn Umar that the Messengerof Allah, may Allah bless him and grant him peace, forbade najsh. Malik said, "Najsh is to offer a man more than the worth of hisgoods when you do not mean to buy them and someone else follows you inbidding." Translation Not Available

Book Ref: Muwatta Imam Malik Book 31 Hadith 1384
Web Ref:  Muwatta Imam Malik Book 31 Hadith 98