What is the ruling on working in an unlicensed private clinic, and is the money earned from it lawful or unlawful?

It is not permissible to practice work in clinics without a license, due to the recognized religious interest in this matter, and due to the generality of Allah's Almighty saying: "O you who have believed, obey Allah and obey the Messenger and those in authority among you," and His saying: "O you who have believed, fulfill [all] contracts." As for the money earned from working in this clinic, it is not unlawful.