What thou doest, do quickly — This is not a permission, much less a command. It is only as if he had said, If thou art determined to do it, why dost thou delay? Hereby showing Judas, that he could not be hid, and expressing his own readiness to suffer.
Related Commentaries of John 13:27
John 13:27
27 And after the sop Satan entered into him. Then said Jesus unto him,That thou doest, do quickly.