Is it permissible for a doctor to take the extra money from his salary—deposited in the bank through Murabaha—to pay off the debt of a needy man whom the doctor had lent money to? And is it permissible to lend out distinguished usurious money and then dispose of it after repayment?

If the surplus money is usurious interest, it is not permissible for the doctor to take it to pay off his debt owed by someone in hardship, because by doing so, he would be benefiting himself. However, it is permissible for him to give this money to the person in hardship, because it is among the permissible expenditures for usurious money. If the person in hardship then uses it to pay off his debt, there is no harm in accepting it.

As for lending out distinctive usurious money and then disposing of it after repayment, this is not permissible, because lending must be from what the lender owns, and this money is not owned by him. However, if the borrower is poor and needy, there is no harm in giving him the money by way of ownership.