A vendor imposed a
    condition that a prospective purchaser has to pay him some compensation if he does not buy
Question

                They imposed a condition that if he did
      not buy the product from them, he would have to pay them compensation if they sold it at a
      loss. Is this an invalid condition? For example, he came and said, “I want to buy
      such and such a product” and they said, “We will bring it from America and if
      you do not buy it, and we sell it to someone else at a loss, you will have to compensate
      us because you broke your promise.” Is this an invalid condition?
Praise be to Allah.We put this question to Shaykh Muhammad ibn Saalih
    al-‘Uthaymeen, may Allaah preserve him, who answered as follows:
Yes, this is an invalid condition.
And Allâh knows best.