[The Presence of Two Wills for a Deceased Person]

Answer – and Allah is the One who grants success: What is obligatory is to execute the last will, and the children are not obliged to execute both wills; rather, it suffices to execute the latter one. We say this by way of judgment in accordance with what normally occurs: a person does not write a second will except when his opinion has changed from what was in the first will. It is extremely far-fetched that he would bequeath one-third of his wealth to Zayd in the first will, then bequeath one-third of his wealth to ʿAmr in the second will, and intend both matters together. Based on what we have mentioned, the one-third of the estate belongs to ʿAmr, not Zayd.
If it is said: The one-third was definitively established for Zayd by the first will, and definitively established for ʿAmr by the last will, so the one-third should be divided between them in halves, acting upon both wills; and it is not permissible to deprive Zayd, the beneficiary of the first will, without a decisive proof eliminating what was established for him in that first will.
We say: It would be definitive that the one-third had been established for Zayd by the first will if the deceased had not subsequently bequeathed that one-third to another man. As for when he has indeed bequeathed it to another man, it is no longer definitive that the one-third remained established for Zayd.
As for when the first will contains bequests relating to injustices and expiations such as zakāt and debts, while the second does not, and it has not become apparent to the heirs that the deceased cleared himself of these obligations, and they have no strong assumption that he did, then what is closer to correctness is that they should carry out what is mentioned there for two reasons: First: In order to clear their deceased’s liability. Second: Because those mentioned rights are attached to the property; thus they must be taken from the estate even if the deceased did not bequeath them, whenever it is known that they remain due in his liability. Allah the Exalted has said: “After any bequest you make or debt.” [al-Nisāʾ:12] And the term “debt” can include expiations, zakāt, monetary debts, and the wrongfully taken property of others.
If it is said: Perhaps the deceased omitted mention of these rights in the second will because he had already discharged them, or for some similar reason.
We say: The basic presumption is that the obligation remains; one should not rule it removed unless the heirs attain knowledge or a strong assumption that the deceased has actually fulfilled what the first will mentioned. If they have neither knowledge nor strong assumption of that, it is obligatory for them to pay out what the first will contained of such rights, as we have mentioned.
As for when the first will contains a bequest for Hajj: If the deceased had already performed the obligatory Hajj of Islam, then his omission of mention of Hajj in the second will is evidence that he has retracted that bequest for Hajj. But if the deceased had not performed the obligatory Hajj of Islam, then it is proper for the heirs to have Hajj performed on his behalf, in order to clear his liability.
This is when it becomes clear to them that Hajj was obligatory upon him and he did not perform it. As for when it becomes clear that Hajj had not yet become obligatory upon him, then they are not obligated to have Hajj performed on his behalf, because at that point the obligation of Hajj was not in his liability.
The proof for this issue and the one before it is what has been narrated from the Prophet, May Allah bless him and his family and grant them peace, that he said: “… So the debt owed to Allah has more right to be repaid.”
Yes, all that we have mentioned here applies in the case where the heirs know which of the two wills preceded the other. As for when the dates of the two wills are unknown, and they do not know which is earlier and which is later, or when one of them is dated and the other undated, then what is required is to divide, for example, the one-third (in the earlier example) between Zayd and ʿAmr, and to act upon what both wills contain—except in matters that are duplicated, where it suffices to act upon one of the two, such as when both wills contain the bequest for one Hajj: one Hajj is sufficient. The same applies to expiations, zakāt and wrongs done to people’s property when the two wills are identical in that; but if one will mentions more of these rights than the other, then it is obligatory to pay the additional amount as well.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2