[Bearing witness to divisions of inheritance (al-qisāmāt) and other than them]

The answer: Allah, Exalted, has legislated the bearing of witness over transactions between people – such as sales, leases, and divisions – out of fear of denial.
If the brothers divide among themselves, with mutual consent and choice, the division is valid, and there is no problem upon them if they do not call witnesses to the division. However, should they later quarrel, the judge will rule by an oath upon the claimant to validate the division – and this is the completing oath (al-yamīn al-mutammimah) – because the scribe is considered a witness; or he will rule by an oath upon the denier to validate the division. If there is testimony regarding the division, there will be no need for oaths; and litigation and quarrelling may not arise in the first place because of the writing and the witnesses.
- It is permissible for the witness to testify even if he does not know the specific item sold or the property divided, and that is by bearing witness to the confession of the two contracting parties regarding the sale, the price, the payment, the receipt, and the sold item, even if he has not seen any of that. This is because the confession and acknowledgment from both parties, and their satisfaction with what the contract contains of details, is sufficient. Likewise in the matter of (property) divided, the witness testifies to what the co-dividers have accepted, acknowledged, and fully and finally agreed upon of the specification mentioned in the written document between them; it is not a condition that the witness know the very items that were divided.
- His testimony, therefore, is to their satisfaction with what the division document contains of details, specification, and so on.

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