Is it permissible to pay Zakat on wealth from bank interest on an amount that has reached the nisab, when the questioner has no other income, and is it permissible to give this Zakat to a brother with a weak income?

If the money is deposited in a usurious bank, it must be withdrawn immediately and placed in an Islamic financial institution or invested in a permissible manner. One must repent from the usurious deposit. If the money reaches the nisab (minimum threshold) and a full hawl (lunar year) passes over it, then zakat is obligatory on it, which is one-quarter of one-tenth (2.5%). The zakat on usurious interest is not permissible; rather, it must be disposed of by spending it on the welfare of Muslims. However, if the money is invested in an Islamic bank, the profit follows the principal in zakat; thus, zakat is calculated on the principal added to the profit. It is permissible to give zakat to one's brother if he is deserving of it, as he has a greater right to it.