Are you certain? Please quote a specific ayyat or hadith that says so. Bidding has long been a means of selling among the Arab people and continues to be so even today in many Arab nations. It is not a form of gambling it is a buyer saying what he is willing to pay and the seller being free to sell to which ever bidder he chooses to sell to, most will choose to sell to the highest bidder. In an honest auction no buyer will ever pay more than he is willing to pay and no seller will sell for less than what he is willing to sell for.