To what extent is it permissible to subscribe to the bank's solidarity fund, which deducts a percentage from the salary to provide assistance after retirement or death, and does it involve any Sharia doubt?

Doubt is added to social security dealings if the funds are invested in usurious banks, resulting in usurious interest. The participant is not permitted to benefit from it; rather, they must dispose of it by giving it to charitable organizations. This applies if participation is mandatory. However, if it is voluntary, then participation is not permissible in the first place. Furthermore, it is not permissible to work in usurious banks due to the cooperation in sin and transgression involved.