What is the ruling on the salary of a private sector employee who retired due to medical disability but is still practicing his profession?

There is no blame on your colleague for receiving a disability pension if he did not lie in the medical report and met the company's conditions, for Allah Almighty says: "O you who have believed, fulfill [all] contracts," and for the Prophet (peace be upon him) saying: "Muslims are bound by their conditions." However, if he lied in the report or did not meet the conditions, he is sinful and does not deserve the pension.