John Calvin Commentary John 5:33

"Ye have sent unto John, and he hath borne witness unto the truth." — John 5:33 (ASV)

You sent to John. Before producing the testimony of God, he presses them with the answer of John, from which they could not honorably withhold their belief. For of what use was it to send to him if they did not intend to abide by his words? They send to him as a Prophet of God, and thus they pretend that his word will be regarded by them as an oracle.

Now, though this implies another admission in their favor, Christ still openly brings this charge against them: that nothing but their own malice hinders them from believing. And, therefore, we see that this circumstance is highly appropriate to the matter at hand—namely, that they sent to John and, as if their motive had been a desire to learn, inquired of him who was the Messiah, and yet paid no attention to his reply.