What is the ruling on money taken by a person for himself after he was asked to bring a worker and agreed with him on a certain wage, then he took a larger amount from the employer than what the worker was owed?

It appears that this person authorized you to bring the worker and agree on his wage, without any agreement on a commission for you or his knowledge that you would take a fee for that. Therefore, you are not permitted to take anything from his money without his consent. What you took in excess of the worker's wage, you are obligated to return to this person.