What is the ruling on a person being employed by a company, then leaving a friend of his to work in his place without the company's knowledge, and what is the ruling on the salary he receives?

What the employee did, deputizing another to work without the company's knowledge, is considered deceit, fraud, and forgery. This is because he is a special hire, obligated to be present at work himself, as his benefit is tied to time, and he does not have the right to deputize. The jurisprudential rule states that whoever is hired for a specific, designated task may not deputize another. However, whoever is hired for a task in which direct personal performance is not stipulated may appoint someone else in his place. The employee must repent and stop this deception, inform the company, or have the original employee return to his work. The salary he received is in exchange for the work that was accomplished, while the salary of the substitute employee is the responsibility of the original employee.