Is it permissible for me to perform Hajj while I am in debt, knowing that the creditor said, "Pay at your leisure"?

Performing Hajj is valid for someone who owes a debt. However, if the debt is due, then the permission of the creditor is required for the debtor to go for Hajj, and the creditor has the right to prevent him. But if the debt is deferred or the debtor is in straitened circumstances, then it is permissible to travel for Hajj without the creditor's permission. It is obligatory to prioritize paying off a due debt over Hajj if you cannot combine both, as capability is a condition for Hajj to be obligatory. The creditor's statement, "Pay at your convenience," means deferring the debt, so there is no sin upon you for performing Hajj while owing it.