Is it permissible to purchase an apartment using the described installment system, given the presence of a penalty clause stating the confiscation of one-third of the amount paid in the event of default on installment payments?

Purchasing an apartment in installments is originally permissible. The penalty clause stipulating that the remaining installments become due upon the buyer's default in payment is also permissible. However, a penalty clause that involves confiscating one-third of the paid installments along with rescinding the sale and repossessing the apartment is forbidden. It is not permissible to enter into a contract that includes this forbidden condition.