What are the Islamic rules for lending money?

“Qardh-e-Hasanah is an interest free loan. In qardhul hasan, the borrower only repays the principal amount. In principle, it is permissible to waive of a loan as a gift or donation.1”

“The difference between a Qardh and a Dayn is that Dayn is more comprehensive while Qardh is more specific. Hereunder are their definitions: Qardh: Loan of Mithli articles (such as money) with the stipulation to return its like in the future.”

“A.A creditor cannot ask his debtor to pay him back his loan in accordance to the rate of inflation over the previous years as the excess amount will be Haraam and tantamount to Riba (interest).”

“This enters under the definition or riba (interest). Hence, it is not permissible. The extra money earned through a loan is riba (interest).”