The ruling on baṣā’ir (written deeds) whose scribe and witnesses have died

The answer – and Allah is the One who grants success – is as in the marginalia of Sharḥ al-Azhār: that baṣā’ir which establish a right among rights, whose witnesses are those whose religiousness and trustwor-thiness are known, are acted upon according to the Sacred Law, even if their scribe and witnesses have died – but on condition that this is joined by the established possession (thubūt al-yad) of that right. As for when the baṣīrah concerns a right over which its owner has no (actual) possession, then it carries no ruling, no reliance is placed upon it, and it is not acted upon according to the Sacred Law. This is what our Imām al-Hādī ʿIzz al-Dīn ibn al-Ḥasan (may Allah have mercy on him) used to adopt… and so on. (Taqrīr) (Í). End of quotation from the marginal note.
I say: The more fitting course is to distinguish in the ruling on a baṣīrah whose owner has no (actual) possession of what it contains of right. That is: what is required of the judge is to look into the circumstances of the owner of the baṣīrah. He may have been, at the beginning of his life, an orphan who did not manage his own wealth, which may have led to some of his relatives, or his guardian, or others taking possession of some of his wealth. Or the owner of the baṣīrah may live outside his homeland. Or it may be the habit of the owner of the baṣīrah to buy property in any land and then sharecrop it, or the like – such that the money leaves his hand, as scholars occupied with knowledge often do: they may earn some money and then hand it over to one of the farmers as a sharecropping partnership. In such a case, what is required of the judge is to act upon the baṣīrah that establishes the right, even if the right itself is not in the hand of the owner of the baṣīrah.
This is so when the baṣīrah is sound: that the handwriting is known and the witnesses are upright. For the judge, (strong) presumption of its soundness is sufficient, since attaining certainty in that is not possible.
If it is said: What is the judge to do then?
We say: The judge demands of the one whose hand over the disputed matter is established that he present the reasons for ownership of that which is disputed: that is, either upright testimony, or documents bearing upright testimony with known handwriting. If the one in possession presents what indicates ownership – either testimony or a baṣīrah – then acting upon that is preferable, due to the joining of established possession with the baṣīrah, and at that point acting upon the baṣīrah that is in the hand of the claimant is abandoned. This is in the case where the two baṣā’ir are in conflict.
As for when the two baṣā’ir are not in conflict – such as when the baṣīrah of the claimant states that the claimant bought what it contains from the one in possession, and the denier does not present anything which conflicts with that – then acting upon it in that case is preferable.
In summary: what is required of the judge is to take into consideration a sound baṣīrah, whose scribe and witnesses are known, even if established possession is not joined to it; and he must treat it as living testimony and place it in the same category, except that it is a little weaker. It is therefore placed at least in the position of a single witness, and thus requires that the claimant strengthen it with an oath. As for discarding it completely, that is not appropriate, for it contradicts what is known of the practice of the Muslims, in ancient times and in more recent times. The Messenger (May Allah bless him and his family and grant them peace) used to send written letters to convey the call to Allah – as in his letters to the king of Persia, the king of Egypt, the king of Rome, the king of Abyssinia, and so on –
and to convey the legal rulings, as in the famous letter of ʿAmr ibn Ḥazm; then the Companions after him, then the Muslims up to today. Among that is the writing of knowledge and ḥadīth and recording them on scrolls; and before that is what Allah, Exalted, has related of the letter of Sulaymān (Peace be upon him) to the Queen of Sheba.
From this Allah, Exalted, has shown His favour upon the servants, saying, Glorified be His Majesty: "Recite in the name of your Lord who created – created man from a clinging clot. Recite, and your Lord is the Most Generous, who taught by the pen, taught man that which he knew not." [al-ʿAlaq:1–5] And He, Glorified and Exalted, has sworn, saying: "Nūn. By the pen and what they inscribe." [al-Qalam:1]
And He, Glorified, has directed His servants to record debts in writing, and for that He revealed the longest verse in the Qur’an, which is called the Verse of Debt at the end of Sūrat al-Baqarah.
For that reason we have said: it is not appropriate to discard sound documents whose owner does not have (actual) possession over what they concern; for that would be to discard the benefit of documentation in writing, whose validity is known, in ancient times and more recent times.
We have only said that they are weak and therefore need to be strengthened by an oath, because of what has come in the verse in Sūrat al-Mā’idah, which is His saying, Exalted: "O you who have believed, testimony between you when death approaches one of you at the time of bequest…" [al-Mā’idah:106] up to His saying, Exalted: "But if it is found that those two were guilty of sin, then let two others stand in their place from among those who have a lawful claim against them, and let them swear by Allah, ‘Our testimony is truer than their testimony, and we have not transgressed. Indeed, we would then be of the wrongdoers.’" [al-Mā’idah:107]
In this verse, and in the story for which it was revealed, there is consideration of writing. It has been related that the heirs of the deceased found a sheet which the deceased had written, in which the wealth and goods that were with him at the time of his death were recorded. When his heirs saw that register, they demanded from the executors of their deceased what was missing. Allah, Exalted, ruled that they should swear an oath concerning what they claimed – that is, concerning what was missing from that which their deceased had recorded in a sheet which he had placed among the goods.
If it is said: Neither in the verse nor in the story has the consideration of writing been mentioned.
We say: The reports that spoke about this story have unanimously mentioned the writing of the deceased’s bequest, and that it was this which revealed to his heirs the missing goods. In the context of the story, the heirs had accepted the oaths of the executors; but when they saw the sheet that the deceased had written among the goods, they returned to demand what was missing, relying on what they saw of the writing. When they made their claim a second time before the Messenger (May Allah bless him and his family and grant them peace), he did not persuade them that the judgment by the oaths of the executors had already been concluded, nor that the writing was not acted upon, nor that it was not permissible for them to rely upon it. Rather, he approved their claim, to which what they saw of the writing had led them, and he requested from them oaths concerning what they claimed.
From this we have said: The verse in Sūrat al-Mā’idah and its story support what we have mentioned. So when the owner of the baṣīrah joins an oath to his baṣīrah, he becomes entitled, by that, to what is in dispute; and if he does not swear, then the denier swears.

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