Matthew 21:25

25Whence was the baptism of John? Christ interrogates them about the baptism of John, not only to show that they were unworthy of any authority, because they had despised a holy prophet of God, but also to convict them, by their own reply, of having impudently pretended ignorance of a matter with which they were well acquainted. For we must bear in mind why John was sent, what was his commission, and on what subject he most of all insisted. He had been sent as Christ’s herald. He was not deficient in his duty, and claims nothing more for himself than to

prepare the way of the Lord.
(Malachi 3:1; Luke 7:27.)

In short., he had pointed out Christ with the finger, and had declared him to be the only Son of God. From what source then do the scribes mean that the new authority of Christ should be proved, since it had been fully attested by the preaching of John?

We now see that Christ employed no cunning stratagem in order to escape, but fully and perfectly answered the question which had been proposed; for it was impossible to acknowledge that John was a servant of God, without acknowledging that he was Himself the Lord. He did not therefore shelter arrogant men, (26) who without any commission, but out of their own hardihood, take upon themselves a public office; nor did he countenance, by his example, the art of suppressing the truth, as many crafty men falsely plead his authority. I do acknowledge that, if wicked men lay snares for us, we ought not always to reply in the same way, but ought to be prudently on our guard against their malice, yet in such a manner that truth may not be left without a proper defense.

Baptism denotes here not only the sign of washing, but the whole ministry of John; for Christ intended to draw out a reply, Was John a true and lawful prophet of God, or an impostor? Yet this mode of expression contains a useful doctrine, Is the of John from God, or from men? For hence we infer, that no doctrine and no sacrament ought to be received among the godly, unless it be evident that it has come from God; and that men are not at liberty to make any invention of this nature. The discourse relates to John, whom our Lord, in another passage, raises, by a remarkable commendation, above all the prophets, (Luke 7:26.) Yet Christ declares that his baptism ought not to be received, unless it had been enjoined by God. What, then, must we say of the pretended sacraments, which men of no authority have foolishly introduced without any command from God? For Christ plainly declares by these words, that the whole government of the Church depends on the will of God in such a manner, that men have no right to introduce any thing from themselves.

But they thought within themselves. Here we perceive the impiety of the priests. They do not inquire what is true, nor do they put the question to their own conscience; (27) and they are so base as to choose rather to shuffle than to acknowledge what they know to be true, that their tyranny may not be impaired. In this manner, all wicked men, though they pretend to be desirous of learning, shut the gate of truth, if they feel it to be opposed to their wicked desires. So then Christ does not allow those men to go without a reply, but sends them away ashamed and confounded, and, by bringing forward the testimony of John, sufficiently proves that he is furnished with divine power. (28)