Maliks Muwatta Book 031, Hadith Number 098.

Section : What is Forbidden of Haggling and Transactions.

Malik said, from Nafi from Abdullah ibn Umar that the Messenger of Allah, may Allah bless him and grant him peace, 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."