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."

قَالَ مَالِكٌ عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ النَّجْشِ .