Ruling on the sale of a pledged item by the pledgor

Question:
I borrowed from the mortgage bank on a piece of land I owned. After I received the first installment of thirty thousand, a man came to me and paid me twenty thousand along with the thirty thousand, and I sold him the land. He borrowed against it in my name and moved in, but he did not pay the bank, even though the agreement was that he would pay the bank. Please give us a ruling, me and whoever is listening, because this method is commonly used by many people?

Answer:
What we know is that the land is pledged to the bank, and it cannot be sold, nor does the bank permit it to be sold, except with its permission, or by paying off the debt owed by its owner. The pledgor has the right to prevent the sale, and the owner of the pledge—the one who owns the land—has no right to dispose of it until he obtains the permission of the pledgee.
The intended meaning: This is pledged money, so he must agree with the bank on this matter. If the bank permits him to sell it to so-and-so, or if so-and-so takes his place, then there is no blame on him. Or if the state permits it and grants people permission, then there is nothing wrong with it.