What is the ruling on buying a house through a bank if the seller pays 30% of its value to the bank without interest, on the condition that the bank sells it to the buyer in installments?

It is not permissible for the seller to lend the buyer a sum of money so that the bank can purchase the house from him, because this loan is considered a loan that draws benefit for the seller, and lending is only permissible purely for the sake of Allah. Furthermore, for the purchase of a house through a bank to be permissible, the conditions of Sharia-compliant Murabaha must be met, such as the bank genuinely owning and guaranteeing the house, and then selling it to the buyer without a prior obligation for the buyer to purchase it.