Matthew Henry's Concise Commentary

20:1-8 Men often pretend to examine the evidences of revelation, and the truth of the gospel, when only seeking excuses for their own unbelief and disobedience. Christ answered these priests and scribes with a plain question about the baptism of John, which the common people could answer. They all knew it was from heaven, nothing in it had an earthly tendency. Those that bury the knowledge they have, are justly denied further knowledge. It was just with Christ to refuse to give account of his authority, to those who knew the baptism of John to be from heaven, yet would not believe in him, nor own their knowledge.