[A man sent payment with a trusted messenger; both the messenger and the payee later died]

Answer—and Allah grants success: If the messenger was trustworthy and just, and a long period elapsed between dispatch and their deaths, then the preponderant presumption is that the messenger delivered the payment. A faithful, upright person does not neglect a trust; if prevented from delivering it, he would typically leave instructions and emphatic directions so it reaches its owner. The absence of any such indications supports that the payment reached its owner.
If it is objected: “The debt is certain; one’s liability is not lifted by mere presumption,”
We reply: The Sacred Law obliges acceptance of the report of a trustworthy just person in transactions. The Prophet (May Allah bless him and his family and grant them peace) would dispatch individuals to collect zakāt and distribute it to the poor; Allah’s Messenger also sent ʿAlī (ʿalayhi al-salām) with funds to Banū Juḏaymah to compensate for those Khalid b. al-Walīd had killed; he distributed compensation among them, compensated them for what they missed, and what was taken from them, even down to the value of a dog’s bowl—and thereby the Prophet’s(May Allah bless him and his family and grant them peace) and the Muslims’ liabilities were cleared.
If it is said: “The Prophet (May Allah bless him and his family and grant them peace) knew ʿAlī (peace be upon him) would fulfill the task due to what Allah Almighty revealed to him of his protection”.
We say: The Prophet (May Allah bless him and his family and grant them peace) legislated by word and deed as Allah, Exalted is He, said “You have in them an excellent example” [al-Mumtaḥanah:6]—and there is no proof from the Prophet, May Allah bless him and his family and grant them peace, that indicate that his reliance on ʿAlī (Peace be Upon Him) in distributing of what was allocated to the Banū Juḏaymah was due to a special privilege given exclusively to Ali (peac be upon him) and not to anyone else; therefore, it became obligatory to follow the Prophet, May Allah bless him and his family and grant them peace, in that matter.
Cases where the sender’s liability is not cleared:
1. It later emerges the messenger was not just/trustworthy—or the sender already knew that the messenger was unjust from the beginning.
2. The sender has credible reason to suspect the payment did not reach the creditor.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2