Romans 2:21

"Thou therefore which teachest another, teachest thou not thyself?" But there he frames his speech with more of sharpness, here with more of gentleness. For he does not say, However on this score thou deservest greater punishment, because though entrusted with so great things thou hast not made a good use of any of them, but he carries his discourse on by way of question, turning them on themselves, and saying, "Thou that teachest another, teachest thou not thyself?" And here I would have you look at the discretion of Paul in another case. For he sets down such advantages of the Jews, as came not of their own earnestness, but by a gift from above, and he shows not only that they are worthless to them if neglectful, but that they even bring with them increase of punishment. For neither is the being called a Jew any well doing of theirs, nor yet is the receiving of the Law, nor the other things he has just enumerated, but of the grace from above. And towards the beginning he had said, that the hearing of the Law is valueless unless the doing be thereto added ("for not the hearers of the Law," he says, "are just before God,") but now he shows further still, that not only the hearing, but, what is more than the hearing, the teaching of the Law itself will not be able to screen the teacher, unless he do what he says; and not only will it not screen him, but will even punish him the more.