What is the ruling on purchasing a house under construction by installments directly from the owner, by paying a down payment and the rest of the amount in monthly installments until the installments are completed and ownership is transferred to the buyer's name, and what is the difference between this transaction and Ijara Muntahia Bittamleek (leasing ending with ownership)?

It is permissible to purchase a house under construction, provided its specifications are clearly defined. This is considered a manufacturing contract (Istisna'a). Ownership of the property transfers to the buyer upon the mere conclusion of the contract. It is not permissible to suspend ownership contingent upon the payment of installments. However, it is permissible to stipulate a prohibition on the buyer selling the property until they have paid what is due. The buyer may obtain documentation confirming the transfer of ownership to them, such as registering a preliminary contract. The official registration of the property in their name may be delayed until the installments are paid, to ensure payment of the price. The difference between this sale and a lease ending in ownership (ijara muntahiya bi al-tamleek) is that here, you purchase the house and its ownership transfers to you immediately, whereas in a lease ending in ownership, you lease the usufruct, and the asset remains the property of its owner until the end of the term. The lease contract may be accompanied by a promise to sell or donate after the installments are paid.