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 Messenger of Allah (ﷺ) forbade najsh.
Malik said, "Najsh is to offer a man more than the worth of his goods when you do not mean to buy them and someone else follows you in bidding."
Reference: USC-MSA web (English) : Book 31, Hadith 98
Arabic : Book 31, Hadith 1384