If someone was employed using a forged certificate in a field related to that certificate, then transferred to another department unrelated to the certificate, having repented, would his money be lawful, or is it better for him to leave the job, taking into account his need for that job, the absence of an alternative, and his responsibility to support a family?

If obtaining a genuine certificate is a condition for working in a specific field, then working with a forged certificate is not permissible, due to the Prophet's (PBUH) saying: "Muslims are bound by their conditions," and "Whoever cheats is not of me." One must strive to earn a livelihood through lawful means and not seek what is with Allah Almighty through disobedience. For the ruling on money earned from a job obtained with a forged certificate, please refer to Fatwa (definition) No. 40930.