What is the ruling on the principle of diminishing Musharakah in borrowing from Islamic banks for purchasing a house, where the loan amount is increased on the basis that it is a rent for the share of the lending party until the full amount is repaid, thereby increasing the borrower's share in the property and decreasing the lender's share?

The origin of this transaction is a loan with interest, and this is usury (riba) because the jurisprudential rule is that every loan that brings a benefit is usury. Even though the hadith (prophetic tradition) mentioning this is weak, the prohibition of a loan that brings benefit has been authentically reported from some Companions. Paying 5,0 dinars as rent is a type of legal trick (hila) that does not change the reality of the contract, nor does it remove it from being usury. Whoever buys a property owns it from the moment of the contract, and therefore cannot be asked to pay rent for it. If the intention is a lease ending in ownership (ijara muntahiya bi al-tamleek), then this is invalid.