No one would question John's greatness, which is why the Evangelist adds,
"And all the people who heard this, including the tax collectors, acknowledged the justice of God, because they had been baptized with John’s baptism."
And yet,
"But by refusing to be baptized by him, the Pharisees and the lawyers rejected God’s purpose for themselves."
Jesus continues,
"'O what then will I compare the people of this generation, and what are they like? They are like children sitting in the marketplace and calling to one another,
"We played the flute for you, and you did not dance;
we wailed, and you did not weep."
For John the Baptist has come eating no bread and drinking no wine, and you say, "He has a demon"; the Son of Man has come eating and drinking, and you say, "Look, a glutton and a drunkard, a friend of tax collectors and sinners!" Nevertheless, wisdom is vindicated by all her children.'”
For no one was greater born of women, but though John was praised, the hypocrites said, "he has a demon", then when the Son of Man came, whom John spoke about, they said, "Look, a glutton and a drunkard, a friend of tax collectors and sinners."
None greater than John, yet here is One greater, the Son of Man, but they would not receive it. The least one is Christ Himself.
Christ's word μικρότερος means "lesser"; the lesser (Jesus) is greater than the greater (John). Even as John himself had said, "After me comes he who is mightier than I, the strap of whose sandals I am not worthy to stoop down and untie".
See, for example, St. John Chrysostom's commentary on Matthew taken from his 37th Homily:
"Now what He said is like this: "woman has not borne a greater than this man." And His very sentence is indeed sufficient; but if you are minded to learn from facts also, consider his table, his manner of life, the height of his soul. For he so lived as though he were in heaven: and having got above the necessities of nature, he travelled as it were a new way, spending all his time in hymns and prayers, and holding intercourse with none among men, but with God alone continually. For he did not so much as see any of his fellow-servants, neither was he seen by any one of them; he fed not on milk, he enjoyed not the comfort of bed, or roof, or market, or any other of the things of men; and yet he was at once mild and earnest. Hear, for example, how considerately he reasons with his own disciples, courageously with the people of the Jews, how openly with the king. For this cause He said also, "There has not risen among them that are born of women a greater than John the Baptist."
But lest the exceeding greatness of His praises should produce a sort of extravagant feeling, the Jews honoring John above Christ; mark how He corrects this also. For as the things which edified His own disciples did harm to the multitudes, they supposing Him an easy kind of person; so again the remedies employed for the multitudes might have proved more mischievous, they deriving from Christ's words a more reverential opinion of John than of Himself.
Wherefore this also, in an unsuspected way, He corrects by saying, "He that is less, in the kingdom of Heaven is greater than he." Less in age, and according to the opinion of the multitude, since they even called Him "a gluttonous man and a winebibber;" and, "Is not this the carpenter's son?" and on every occasion they used to make light of Him.
What then?" it may be said, "is it by comparison that He is greater than John?" Far from it. For neither when John says, "He is mightier than I, does he say it as comparing them; nor Paul, when remembering Moses he writes, "For this man was counted worthy of more glory than Moses," does he so write by way of comparison; and He Himself too, in saying, "Behold, a greater than Solomon is here," speaks not as making a comparison.
Or if we should even grant that this was said by Him in the way of comparison, this was done in condescension, because of the weakness of the hearers. For the men really had their gaze very much fixed upon John; and then he was rendered the more illustrious both by his imprisonment, and by his plainness of speech to the king; and it was a great point for the present, that even so much should be received among the multitude. And so too, the Old Testament uses in the same way to correct the souls of the erring, by putting together in a way of comparison things that cannot be compared; as when it says, "Among the gods there is none like You, O Lord:" and again, "There is no god like our God."
Now some affirm, that Christ said this of the apostles, others again, of angels. Thus, when any have turned aside from the truth, they are wont to wander many ways. For what sort of connection has it, to speak either of angels or of apostles? And besides, if He were speaking of the apostles, what hindered his bringing them forward by name? Whereas, when He is speaking of Himself, He naturally conceals His person, because of the still prevailing suspicion, and that He may not seem to say anything great of Himself; yea, and we often find Him doing so.
But what is, "In the kingdom of heaven?" Among spiritual beings, and all them that are in heaven.
And moreover His saying, "There has not risen among them that are born of women a greater than John," suited one contrasting John with Himself, and thus tacitly excepting Himself. For though He too were born of a woman, yet not as John, for He was not a mere man, neither was He born in like manner as a man, but by a strange and wondrous kind of birth." - St. John Chrysostom, Homily 37.2-3
-CryptoLutheran