What is the ruling on a person taking a debt collection for 100,0, to pay off part of it, then collecting the amount from the debtor?

This transaction is the sale of a deferred debt for a lesser immediate cash payment of the same kind. It combines interest by excess (riba al-fadl) and interest by delay (riba al-nasi'ah), similar to the sale of financial instruments. Selling a deferred debt for less than its current value to someone other than the debtor is a form of prohibited usury according to the majority of scholars. Those who permit it impose conditions that are not met here, the most important of which is equivalence when selling debt of the same kind.