Is it permissible to return to work in an auditing firm that audits usurious banks and insurance companies, knowing that the work will be limited to auditing the accounts of industrial and commercial companies?

If your work in auditing companies is permissible and lawful, then there is no blame upon you. However, if it is in the field of accounting for usurious banks or prohibited companies, then it is not permissible, because it is cooperating in sin. Allah Almighty says: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression). The Prophet, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses. A Muslim must seek lawful sustenance and avoid prohibitions and doubtful matters, in accordance with the Almighty's saying: (O you who have believed, eat from the good things which We have provided for you), and the saying of the Prophet, peace and blessings be upon him: "The lawful is clear and the unlawful is clear, and between them are doubtful matters." And whoever fears Allah, He will make his matters easy for him and provide for him from where he does not expect.