Romans 2:21

How is it that ye wish to instruct the elect of the Lord, while ye yourselves have no instruction? Instruct one another therefore, and be at peace among yourselves, that I also may stand joyful before your Father, and give an account of you all to the Lord.

"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.

Then when he says you who teaches another, he indicates some of their failings. First, failings toward themselves, when he says you who teaches another, by directing them to the good, teaches not yourself. This can be taken as a question asked with an overtone …

He presents his thought in the form of a question, shaming those who boasted that they were teachers.

He now inverts the order: for sins against God are the most glaring in an heathen, but not in a Jew. Thou that abhorrest idols - Which all the Jews did, from the time of the Babylonish captivity. Thou committest sacrilege - Doest what is worse, robbing Him "who is God over all" of the glory which is due to him.

The greatest obstructors of the success of the word are those whose bad lives contradict their good doctrine, who in the pulpit preach so well that it is a pity they should ever come out, and out of the pulpit live so ill that it is a pity they should ever come in. He specifies three particular sins that abound among the Jews:-- (1.) Stealing.

Thou therefore which teachest another, teachest thou not thyself?....

Behold--"But if" is, beyond doubt, the true reading here. (It differs but in a single letter from the received reading, and the sense is the same).

Thou therefore - Dr. Taylor has paraphrased this and the three following verses thus: “What signify your pretensions to knowledge, and the office of teaching others, if you have no regard to your own doctrine? What are you the better for preaching against theft, if you are a thief yourself? Or for declaring adultery unlawful, if you live in the practice of it? Or for representing idolatry abominable, if you are guilty of sacrilege? What honors or singular favors do you deserve, if, while you glory in the law and your religious privileges, you dishonor God, and discredit his religion, by transgressing his law, and living in open contradiction to your profession? And this is more than supposition; notorious instances might be produced of the forementioned crimes, whereby the Jews of the present age have brought a reproach upon religion among the Gentiles; as well as those Jews of former times, of whom the Prophet Ezekiel speaks, Eze 36:23: And I will sanctify my great name, which was Profaned among the Heathen, which ye have Profaned in the midst of them.” That the Jewish priesthood was exceedingly corrupt in the time of the apostle, and that they were so long before, is fully evident from the sacred writings and from Josephus. The high-priesthood was a matter of commerce, and was bought and sold like other commodities. Of this Josephus gives many instances. The rapine of Eli’s sons descended to several generations. Dr. Whitby well observes that of all these things mentioned by the apostle the Jewish doctors were notoriously guilty; and of most of them they were accused by our Lord. 1. They said and did not; and laid heavy burdens upon others, which they would not touch with their own fingers, Mat 23:3, Mat 23:4. 2. They made the house of God a den of thieves, Mat 21:13; Joh 2:16. 3. They were guilty of adultery by unjust divorces, Mat 19:9. 4. […]

Thou therefore ... - He who is a teacher of others may be expected to be learned himself. They ought to be found to be possessed of superior knowledge; and by this question the apostle impliedly reproves them for their ignorance. The form of a question is chosen because it conveys the truth with greater force.