Firstly, the value of the work performed by this laborer for you is a debt upon you, obligatory to fulfill, whether it is paid to him or to his heirs. The evidence for this is the well-known Ḥadīth concerning the three people.
Secondly, if there is a considerable time gap or a difference in the currency value between the completion of the work and the time of payment, the calculation depends on the value, not the actual item’s price. This applies to all financial obligations that are deferred, such as a woman’s dowry, a long-overdue debt, or money wrongfully withheld for an extended period.
Therefore, you must estimate the value of his wages in terms of gold at the time the work was done and pay him or his heirs an equivalent amount based on the current price of gold.
After all, Allāh knows best.
Fatwa issued by Dr. Khālid Naṣr