What is the ruling on working and training in a usurious, non-Islamic bank for the purpose of gaining experience that would qualify one to work in an Islamic bank in the future, and is the salary earned from this work unlawful or not?

Working in usurious banks is impermissible due to its nature of aiding in sin and aggression. A curse has been pronounced upon everyone involved with Riba (usury), including its devourer, its consumer, its scribe, and its two witnesses; they are all equal in sin. This prohibition encompasses all positions, even security and cleaning, because they are considered assistance to other employees in their usurious activities. It is also impermissible to train in these banks or work as a driver or guard, because working there necessitates consenting to this forbidden work. A Muslim must avoid this work and seek lawful earnings. Money acquired from such work must be disposed of by spending it on the poor, the needy, and other charitable causes.