Is it permissible to sell an apartment to someone who buys it through a mortgage (usurious loan), where the price is paid to the seller by the bank via a mortgage contract, knowing that the bank grants a loan and does not buy the apartment for itself? And does the ruling differ if the buyer comes with cash obtained from the usurious bank?

It is not permissible for a person to assist someone who intends to engage in a usurious transaction by facilitating it for them, due to the Almighty’s saying: "O you who have believed, fear Allah and give up what remains [due to you] of usury, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged." And the Prophet (peace and blessings be upon him) "cursed the one who consumes usury, the one who gives it, and its two witnesses, and he said they are all equal." As for selling an apartment to someone who took out a usurious loan, and the seller was not a party to the loan, there is no objection to it.