According, &c. This law was to be the rule of the priests, in passing sentence. It was not left to the judgment of individuals to comply or not, according as they might explain the law for themselves. Such a proceeding would be nugatory, as they would thus be themselves the ultimate judges of their own cause. (Haydock)

They shall seek the law at his (the priest’s) mouth, Malachias ii. 7. Protestants make, therefore, a very frivolous restriction, when they allow his sentence to bind only “so long as he is the true minister of God, and pronounceth according to his word.” (Bible, 1603.) (Worthington)

If any had been proud enough among the Jews, to persuade himself that he understood the law better than the high priest, he would not on that account have escaped death. (Haydock)

The authority of the Christian Church is not inferior to that of the Synagogue, only, “instead of death, excommunication is now inflicted” on the rebellious. (St. Gregory, Matthew xviii. 17.; St. Augustine, q. 38.) In effect, St. Paul assures us that the priests of the law, serve unto the example and shadow of heavenly things. But now he (Christ)...is the mediator of the better covenant, which is established on better promises, Hebrews viii. 5, 6. If therefore the privilege of deciding points of faith and morality, without danger of mistake, was granted to the synagogue, can any one doubt but that Christ would provide as ample a security for his Church, with which he has promised to remain for ever, and with his Holy Spirit to teach her all the truth? (Haydock)

St. Augustine dwells upon this argument (Doct. 4.) and proves the infallibility both of the Jewish and of the Christian Church. Hence Christ said, with respect to the former, which was not yet rejected, All therefore whatsoever they shall say to you, observe and do: but according to their works, do ye not: for they say the truth, and do not practise what they require of others. If the heads of the Catholic Church should be equally immoral, their true doctrine must not therefore be despised, lest Christ and his Father be at the same time despised. For this is the express admonition of our heavenly lawgiver, hear the Church: (Matthew xvii. 17,) and this he does not require without giving us a full assurance, that we may do it without fear of being led astray. The sole command of God implies as much, if he had said no more. For can he order us to sin? The pretended reformers, who blushed not to make this blasphemous assertion, might easily swallow down the other, respecting the defection and fallibility of the whole Church; and might even believe, that the whole world had been drowned in abominable idolatry for eight hundred years and more. (Hom. on the peril of idolat. p. 3.) How much more they do not determine, lest they should be forced to tell when the religion of the Catholics began, and that they will never do without dating from Christ and the apostles, the foundations of the only true Church. (Haydock)

The Jews had such a respect for the decisions of their Rabbins, in consequence of this command of God, that some hesitate not to assert, that if one of them should declare that the left hand was the right, they would believe him; and they condemn the refractory to most grievous torments in hell. (Buxtorf., Syn. i.)

We must shew the most profound submission to the decrees of the Church. (Calmet)

Yet we are not bound to assent to the decisions of every teacher. Only, when the Church speaks, we must not refuse to obey, nor pretend to appoint ourselves judges of what she teaches. A private doctor, however eminent, may fall into some absurdities, but the major part of the pastors of the Church, with the Pope at their head, never can. In vain have the records of nineteen centuries been ransacked, to find a single instance of such a general agreement in error. If the Synagogue passed a wicked sentence upon Jesus Christ, we must reflect that the forms here required (ver. 8,) were neglected; and it was then expiring, and giving place to a better covenant, as the prophets had foretold. Yet even in that sentence, which was so unjust on the part of Caiphas, St. John (xi. 51.) acknowledges the truth of God. And this he spoke not of himself: but being the high priest, that year, he prophesied that Jesus should die for the nation, and not only for the nation, but to gather together in one the children of God that were dispersed. The Synagogue could claim submission no longer, after the great prophet had come to abrogate the law of fear, and to substitute that of love. Hence while he was there to teach himself, (Hebrews i. 2,) there was no danger of deception for the people. But the covenant which he has established is to last for ever: no prophet or lawgiver is promised to introduce any change, or greater perfection, so that no one can plead for an excuse of his rebellion, that the Church may deceive and pass an erroneous judgment; or, if he do, he must be cut off from the society of the faithful, by the spiritual sword; and, dying in that state, without the Church for his mother, he need never expect that God will acknowledge him for his son. See St. Cyprian, Unity of the Catholic Church. If an individual pastor should pass such a perverse sentence, the case would be very different. Yet, even in such trying cases, an humble conduct will be the best security and proof of innocence, and God will reward those who have suffered unjustly. (Haydock)