Allah’s command to “fulfill (all) obligations” is a general command and it applies to all obligations and covenants, regardless of whether those obligation are with Muslims or to non-Muslims. The command applies as long as the obligation itself is not contrary to the dictates of Islamic Law.
The Prophet (peace be upon him) said: “There are four qualities that if a person possesses them all, he is a real hypocrite, and if he possesses some of them, then he has a share of hypocritical qualities until he abandons them. If he is entrusted, he deceives. If he speaks, he lies. If he makes a commitment, he breaks it, and if he argues, he goes out of bounds.” [Sahîh al-Bukhârî (33) and Sahîh Muslim (59)]
This hadîth gives a stern warning against the breaking of promises. This hadîth, like the verse above, is general. It applies to all promises and pledges, regardless of whether the person with whom he made a promise is a Muslim or a non-Muslim.
One extremely important commitment that deserves mention is that of debt. Those who fail to pay back their debts are given the sternest of warnings. The Prophet (peace be upon him) said: “The martyr is forgiven all of his sins…except for his debts.” [Sahîh Muslim (1886)]
The Prophet (peace be upon him) also said: “The soul of a believer is held tied to its debt until it is paid on his behalf.” [Musnad Ahmad (9302), Sunan al-Tirmidhî (1078), and Sunan Ibn Mâjah (2413)]
Al-Tirmidhî grades it as a good hadîth and al-Albânî grades it as authentic.
These two texts are just as general in their meaning as the one’s mentioned earlier. They apply to all debts, regardless of whether the person being owed is a Muslim or a non-Muslim.
Ibn `Abd al-Barr discusses the second hadîth in his commentary entitled al-Istidhkâr, and writes (5/100):
This hadîth indicates for Islamic Law that fulfilling the debts left by the deceased benefits the deceased in his life of the Hereafter. This is why his successor is commanded to pay off his debt on his behalf and that the estate will not be distributed to the inheritors except after all debts have been paid.Al-Shawkânî also discusses this hadîth in his commentary entitled Nayl al-Awtâr, and says (4/53):
Here, the inheritors are being encouraged to pay off the debts of the deceased and informs them that his soul is suspended by the debts until they are paid off. This circumstance is conditional on the debtor dying while being in possession of wealth to pay towards his debts.These hadîth show us that debts are serious obligations, regardless of the identity of the party to whom the debt is owed. It is obligatory for a Muslim who is in debt to pay off his debts promptly, as soon as they come due, if he is able to pay.
As for a person who dies without possessing any wealth, but who had been determined to pay off his debts, his case is different. There are other hadîth that tell us that Allah will fulfill his debts on his behalf. Indeed, it is established that the mere desire on the part of the dying person to pay off his debts is sufficient for Allah to fulfill them on his behalf.
If he dies, it is forbidden for his inheritors to receive their shares of his estate until all outstanding debts and bequests are satisfied.
Allah says in the verse of inheritance: “…after the payment of bequests that have been bequeathed and the payment of debts.” [Sûrah al-Nisâ’: 12]
If the person who died did not leave behind what will fulfill his debts, it is sanctioned for his successor to pay it off on his behalf, and the deceased will benefit form that.
If the debt in question is an interest loan, then the lender is only entitled to his principal. At the same time, the debtor is also not entitled to the amount of the accrued interest, and he must rid himself of that sum from his own wealth and spend it on the needs of others with the intention of ridding himself of unlawful wealth and not with the intention of spending in charity.
When debts are not paid, they are rights that become due in the Hereafter. The Prophet (peace be upon him_ said: “Rights will be restored to those entitled to them on the Day of Resurrection, so much so that the sheep without horns will receive its reparations from the horned sheep.” [Sahîh Muslim (2582)]
The Prophet (peace be upon him) also said: “Whoever has committed wrong against someone else’s honor or with respect to something else, then let him resolve the matter with him today before it will not be resolved with gold and silver coins – but if he had good deeds to his credit, they will be taken from him to the degree of his wrong, and if he has no good deeds to his credit, then he will be made to assume some of the bad deeds of the one who was wronged.” [Sahîh al-Bukhârî (2449)]
The rights that people have are upheld for them in the Hereafter and are recompensed through good deeds or bad deeds. This applies generally, even between believers and non-believers. As for how Allah will carry this out between believers and non-believers, we cannot know this. When a Muslim has wronged a non-believer, will Allah take away some of the non-believer’s evil deeds and make the Muslim assume them? Or will some of the Muslim’s good deeds and in lieu of them lighten the non-believer’s punishment? Only Allah knows. We are not held accountable to know such matters of the Unseen and we will not be asked about them.
We as Muslims are, however, responsible for our conduct. We are warned against wronging others and making little of our obligations towards others, regardless of what those obligations might be and regardless of who the people are to whom we are obliged.
And Allah knows best.
And may the peace and blessings of Allah be upon the Prophet Muhammad, his family, and his Companions