Musannaf Ibn Abi Shaybah

Hazrat Amr bin Muhajir says that Hazrat Umar bin Abdul Aziz sent Ameero bin Yazid Filastini so that he could auction the prisoners. When he returned after completing the task, Hazrat Umar asked him, "Was there any sale today?" He replied, "O Commander of the Faithful! If I had not personally gone and raised the bids, today would have been a dull day." Hazrat Umar asked him, "Did you bid without the intention of buying, merely to raise the price?" He admitted it, so Hazrat Umar (may Allah have mercy on him) said, "This is najsh; it is not permissible. O Ameero! Announce that the sale is void and najsh is not permissible."