From: Matthew 11:2-11
The Mission of John the Baptist. Jesus' Reply
 Now when John heard in prison about the deeds of the Christ, he sent word by his disciples  and said to him, " Are you he who is to come, or shall we look for another?"  And Jesus answered them. "Go and tell John what you hear and see:  the blind receive their sight and the lame walk, lepers are cleansed and the deaf hear, and the dead are raised up, and the poor have good news preached to them.  And blessed is he who takes no offense at me."
 As they went away, Jesus began to speak to the crowds concerning John: "What did you go out into the wilderness to behold? A reed shaken by the wind?  Why then did you go out? To see a mana clothed in soft raiment? Behold, those who wear soft raiment are in kings' houses.  Why then did you go out? To see a prophet? Yes, I tell you, and more than a prophet.  This is he of whom it is written, 'Behold, I send my messenger before thy face, who shall prepare thy way before thee.'
 "Truly, I say to you, among those born of women there has risen no one greater than John the Baptist; yet he who is least in the kingdom of heaven is greater than he."
2. John knew that Jesus was the Messiah (cf. Mt 3:13-17). He sent his disciples to Jesus so that they could shed their mistaken notions about the kind of Messiah to expect, and come to recognize Jesus.
3-6. Jesus replies to the Baptist's disciples by pointing to the fact that they are witnessing the signs which the ancient prophecies said would mark the advent of the Messiah and his Kingdom (cf. Is 35:5, 61:1; etc). He says, in effect, that he is the prophet who "was to come".
The miracles reported in the Gospel (chapters 8 and 9) and the teaching given to the people (chapters 5-7) prove that Jesus of Nazareth is the expected Messiah.
6. Jesus here corrects the mistaken idea which many Jews had of the Messiah,
casting him in the role of a powerful earthly ruler--a far cry from the humble attitude of Jesus. It is not surprising that he was a stumbling block to Jews (cf. Is 8:14-15; 1 Cor 1:23).
11. With John the Old Testament is brought to a close and we are on the threshold of the New. The Precursor had the honor of ushering Christ in, making him known to men. God had assigned him the exalted mission of preparing his contemporaries to hear the Gospel. The Baptist's faithfulness is recognized and proclaimed by Jesus. The praise he receives is a reward for his humility: John, realizing what his role was, had said, "He must increase, but I must decrease" (Jn 3:30).
St John the Baptist was the greatest in the sense that he had received a mission unique and incomparable in the context of the Old Testament. However, in the Kingdom of heaven (the New Testament) inaugurated by 'Christ, the divine gift of grace makes the least of those who faithfully receive it greater than the greatest in the earlier dispensation. Once the work of our redemption is accomplished, God's grace will also be extended to the just of the Old Alliance. Thus, the greatness of John the Baptist, the Precursor and the last of the prophets, will be enhanced by the dignity of being made a son of God.
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.