What is the ruling on money taken from a grandfather's pension, which the state contributes to for retirees, knowing that the grandfather has other money that he deposits in a usurious bank?

It has been previously affirmed that it is forbidden to deposit money in postal savings accounts and interest-based banks, because it is not a legitimate investment. The grandfather should be advised and informed of the Sharia ruling. There is no harm in receiving the pension through interest-based institutions.