Is it permissible for the ruler to sell or buy?

The Shaykh : Now, regarding selling and buying, is it permissible for the ruler to sell and buy? Yes, it is permissible. However, the scholars said that he should not personally conduct the selling and buying himself, because he might show favoritism by paying more than the value of the goods or lowering the price of the goods he buys below the fair value. This would constitute favoritism toward him. And what they said is correct, especially if this judge is someone who is known, or it is likely, that if he sells or buys, people will lower the price for him or increase the price if he is the seller, out of favoritism toward him. In that case, he should not personally engage in this matter. If he does engage in it because he has no servant to do it for him, he must be careful to avoid favoritism, and he should not buy except at the fair price, nor sell except at the fair price.