Is it permissible to take time off from one's current job to search for another, compensating for this time from one's salary without the employer's knowledge?

If an employee hires himself out to another party during his original working hours, he must deduct the wage for that time from his salary. If he has not yet made such arrangements, he is not permitted to do so without the employer's permission, because the time stipulated in the contract belongs to the employer.