8 “And they which were sent were of the Pharisees,” that is, of the chief men among the Jews; “and they asked him and said unto him, Why do you baptize then, if you be not the Christ, nor Elias, nor a prophet?” As if it seemed to them audacity to baptize, as if they meant to inquire, in what character do you baptize? We ask whether you are the Christ; you say that you are not. We ask whether you perchance are His precursor, for we know that before the advent of Christ, Elias will come; you answer that you are not.
We ask, if perchance you are some herald come long before, that is, a prophet, and hast received that power, and you say that you are not a prophet. And John was not a prophet; he was greater than a prophet. The Lord gave such testimony concerning him: “What went ye out into the wilderness to see? A reed shaken with the wind?” Of course implying that he was not shaken by the wind; because John was not such an one as is moved by the wind; for he who is moved by the wind is blown upon by every seductive blast.
“But what went ye out for to see? A man clothed in soft raiment?” For John was clothed in rough garments; that is, his tunic was of camel's hair. “Behold, they who are clothed in soft raiment are in kings' houses.” You did not then go out to see a man clothed in soft raiment. “But what went ye out for to see? A prophet? Yea, I say unto you, one greater than a prophet is here;” for the prophets prophesied of Christ a long time before, John pointed Him out as present.
Source: Tractates on the Gospel of John (New Advent)