Dr. Monzer Kahf, a scholar in Islamic economics and a financial expert, who gave the following reply:
“Interest-based loans are not permissible in Shari’ah because interest is a very grave sin as Allah decrees in the Qur’an (2:275-79). Of course when a Muslim is under a loan (regardless of whether it is with interest or not), he/she is expected to give priority to paying back the loan by using all available savings and even by pressing down one’s current expenses. Logically this would not leave any money to go for Hajj.
On the other hand, going for Hajj and paying one’s debts are two separate matters, one does not depend or affect the other and each of them is judged on its own. This means that for a person who is under debt and goes for Hajj, Allah will judge each action on its own merits. If the debt is due and not paid or if it is interest-based, delaying payment is sinful, and going for Hajj is rewardable. Allah said in the Qur’an what means that each action is judged on its own (17:15).”