This depends on the contract you had with him. If he did something that requires a penalty, you can deprive him of his commission but this also depends on the penalty of the policies and procedures of the company!

one kuffar is working with me, during that time i was book supplier, during time he working with me he take use my car to do his own business as book supplier, when i find out then i sack him. the question is i have to pay some commission to him, becouse of this case i stop paying his commission , what should i do?