What is the ruling on participating in paying the blood money for a killer who has confessed to his intentional crime, despite his family's ability to pay the full amount, and is that considered unlawful (haram)?

Scholars have unanimously agreed that the blood money (diyyah) for intentional killing is obligatory upon the killer's wealth and is not borne by the 'Aqilah (the killer's kin group), because the offense is a consequence of the perpetrator's action, and thus he alone is responsible for its harm. This principle was only deviated from in the case of accidental killing due to the large amount owed and the perpetrator's inability to pay. As for neighbors or others assisting the killer in paying the blood money, it is permissible and considered a good deed for which the doer is rewarded.