An equitable inflationary adjustment does not come
under the definition of Ribā as this adjustment is meant to return the full
value of the loan to the lender. It does not aim at giving any fixed,
predetermined, time related gain on that loan.
The Qur’ān indicates that if the borrower has to pay Ribā,
it is exploitation and oppression. Similarly, if the lender is not given his
principal back, that too is exploitation and oppression (2:279).