All perfect praise be to Allah, The Lord of The Worlds, and may His blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
Heirs are obliged to reveal the debts for which the deceased is liable if the latter had informed them about that, or there is evidence proving so, because concealing them is considered eating up peoples` property unjustly. Allah, The Almighty, said, "God doth command you to render back your Trusts to those to whom they are due"{An-Nisaa`/58}.
The debts for which the deceased is liable must be paid after paying the expenses of the burial, but before the division of the estate on the eligible heirs. Here, it is worth noting that the creditors` rights are due from the deceased`s estate, and his heirs aren`t obliged to settle them from their own wealth, but if they did to free him from the liability, then they are considered donors, and they will receive their recompense from Allah. And Allah knows best.
