For your obedience is come abroad unto all men. I am glad therefore on your behalf: but yet I would have you wise unto that which is good, and simple concerning evil. For your obedience is come abroad - The apostle gives this as a reason why they should continue to hear and heed those who had led them into the path of truth, and avoid those false teachers whose doctrines tended to the subversion of their souls.
Yet I would have you wise - I would wish you carefully to discern the good from the evil, and to show your wisdom, by carefully avoiding the one and cleaving to the other.