Pseudo-Chrysostom — as excerpted in the Catena Aurea on Matthew 21:23-27

“Not that they should answer it, and thereupon hear of Christ the answer to their question, but that being puzzled they should ask Him no farther; according to that precept He had given above, Give not that which is holy to the dogs. (Mat. 7:6.) For even if He had told them, it would have profited nothing, because the darkened will cannot perceive the things that are of the light. For him that enquires we ought to instruct, but him that tempts, to overthrow by a stroke of reasoning, but not to publish to him the power of the mystery. The Lord thus sets before them in His question a dilemma; and that they might not escape Him, says, Which if ye tell me, I in like wise will tell you by what authority I do these things. His question is this; The baptism of John whence was it? from heaven, or of men?”