Is it permissible for an engineer to continue his current work of constructing a usurious bank, knowing that his task is limited to arbitrating the contractor's dues, that he cannot find other work, that he supports a family, and that leaving the job would cause embarrassment to his office and to the project owner?

It is forbidden to work in the establishment of usurious banks or to assist them in any way, because this involves dealing with usury, the perpetrator of which, its scribe, and its witnesses have been cursed. Those involved in this are exposed to war from Allah and His Messenger. The people of knowledge have issued fatwas prohibiting work in usurious banks, even if the work itself is not usurious, such as security guarding, because it constitutes assistance in sin. Therefore, this work must be abandoned. Continuing in it is not permissible on the grounds that the project is in its final stages, or that it causes embarrassment or dismissal, for whoever abandons something for the sake of Allah, Allah will compensate him with something better, and sustenance is in the hand of Allah.