Musnad Ahmad 27:84

'Abd al-Rahman narrated to us, Malik narrated to us, from Nafi', from Ibn 'Umar: "That the Prophet, peace and blessings of Allah be upon him, forbade meeting the goods [of merchants] before they reach the markets." And he forbade *al-najash* (bidding up the price without the intention to buy), and he said: "Let none of you sell over the sale of another." "And when he was in a hurry to travel, he would combine the Maghrib and the 'Isha' prayers."