Ruling on getting back a loan from interest-based money

A debtor transferred his debt to an interest-based bank. Is it permissible for the lender to take what he is owed from the bank when he knows that the contract between the bank and the debtor is based on interest?

Praise be to Allah, and blessings and peace be upon the Messenger of Allah:

It may be permissible, because the lender is not a party to the interest-based transaction. But he should try to advise both parties.