What is the ruling on selling land for which not all installments have been paid, for an amount exceeding the first down payment?

It is permissible to purchase lands and goods—excluding gold, silver, and currencies—with a deferred price, whether in full or in part. Upon the completion of the contract, the buyer becomes the owner of the land, and thus has the right to dispose of it by selling or gifting, while continuing to pay the outstanding installments. This is on condition that he does not sell it back to the original seller at a spot price lower than what he bought it for, as this would constitute a forbidden bay' al-'inah (a type of buy-back transaction). However, if the seller stipulates that the land cannot be sold until the full price is paid, this condition is permissible and is considered a pledge (rahn). In this case, the buyer is not allowed to sell it except with the permission of the seller, who is the pledgee. If there is no agreement on a pledge, then the buyer may sell it at any price he wishes.