What is the ruling on banks authorizing others to collect their outstanding debts from people, especially concerning a lawyer?

The ruling on advocacy was previously explained in fatwa no. 30545.

Based on that, if the banks are Islamic, do not engage in usury, and only perform what is Islamically permissible, then there is no harm in working with them as an agent. However, if they are usurious banks, it is not permissible to act as an agent on their behalf to collect their usurious debts, because it is assisting in sin. Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression" [Al-Ma'idah: 2].