Is it permissible to pay off existing usurious loans as charity for repentant borrowers, or is it only permissible to pay off the principal of the loan without the usurious interest?

Whoever repents from usurious transactions and regrets them, and is unable to rid himself of the interest systematically imposed on him, then it is permissible to assist him in repaying this debt and the resulting interest. This is because it alleviates a Muslim's distress, and due to the saying of the Prophet, peace and blessings be upon him: "Whoever alleviates a Muslim's distress, Allah will alleviate a distress from him on the Day of Resurrection." As for whoever does not repent from these usurious transactions, it is not permissible to assist him in repaying his debt, because that would be aiding him in sin and transgression.