Is it permissible for the creditor to oblige the debtor to change the terms of the debt from unspecified duration or written form to a specified duration and written form after several years, contrary to what was previously agreed upon?

Scholars have differed on the issue of postponing loan repayment, holding two opinions:

The first opinion (the majority of jurists): It is not permissible to postpone a loan, and the lender may reclaim it at any time, as deadlines in loans are invalid.

The second opinion (Malikis, Zahiris, and the choice of Ibn Taymiyyah and Ibn Uthaymeen): Postponement is valid if stipulated as a condition. If a term is stipulated in the loan, the borrower is not obligated to repay the money before the specified term expires. They cited the verse: "O you who have believed, when you contract a debt for a specified term, write it down," and the hadith: "Muslims are bound by their conditions."

Accordingly, if the debt is not specified by a term, the lender may demand it immediately or set a term for it. If the term expires and the borrower is able to repay, repayment becomes obligatory, based on the Prophet's (peace be upon him) saying: "Procrastination by a rich person is injustice." If the borrower is in financial difficulty, he must be granted a respite until he finds ease, based on Allah's (the Most High) saying: "And if there is one in [financial] difficulty, then [give him] time until a time of ease."