What is the ruling on the Hajj of a person who borrowed money for Hajj and did not return it to its owner, and what is the ruling on his action?

His Hajj is valid if he fulfilled its pillars, conditions, and obligations. His failure to repay the loan does not affect the validity of the Hajj. If the debtor is procrastinating and able to repay, then he is sinful, as the Prophet, peace and blessings be upon him, said: "The procrastination of the rich is injustice." However, if he is in straitened circumstances and unable to fulfill the payment, there is no sin upon him, and he must be given respite until he can repay, as Allah Almighty says: {And if there is one in [financial] difficulty, then [let there be] a delay until [a time of] ease.}