Is it permissible to agree to pay monthly installments for the purchase of a residential apartment in Lebanese Lira based on the exchange rate of the dollar against the Lira?

Purchasing apartments before their construction on an installment basis falls under the contract of Istisna' (manufacturing contract). The Islamic Fiqh Academy has permitted this with two conditions: the specifications of the apartment must be clearly defined, and the deadline for delivery must be specified, with the permissibility of deferring the entire price or paying it in installments.

However, it is not permissible to link the remaining price to the value of the dollar, as this constitutes deferred currency exchange (sarf). The principle for fulfilling fixed debts in currency is by paying the equivalent amount of the same currency. It is not permissible to link it to price levels, gold, or another currency, as this leads to gharar (uncertainty), jahalah (ambiguity), injustice, and disputes.