When the messengers of John had left, Jesus began to speak to the crowds about John. "What did you go out to the desert to see– a reed swayed by the wind? Then what did you go out to see? Someone dressed in fine garments? Those who dress luxuriously and live sumptuously are found in royal palaces. Then what did you go out to see? A prophet? Yes, I tell you, and more than a prophet. This is the one about whom scripture says: 'Behold, I am sending my messenger ahead of you, he will prepare your way before you.' I tell you, among those born of women, no one is greater than John; yet the least in the kingdom of God is greater than he." (All the people who listened, including the tax collectors, and who were baptized with the baptism of John, acknowledged the righteousness of God; but the Pharisees and scholars of the law, who were not baptized by him, rejected the plan of God for themselves.) (Lk 7:24-30)
Jesus bears witness to John the Baptist. John the Baptist was a prophet and more than a prophet. He was also a messenger. As a messenger he was not just carrying the message but he was also going ahead of the one about whom he was giving the message. He is the forerunner who announces the arrival of the messiah and also he was preparing the people for the arrival.
There was no one who was greater than him. It should be because of the commitment of John the Baptist to the mission. He completed his mission to the perfection and even at the risk of his life. In fact people come searching for him even from the cities. People came to him and were even baptized by him.
All those who were baptized by him accepted God and God’s plan. But eh Pharisees and the scholars of the law rejected the plan of God and thus they were not in the kingdom. The tax collectors and sinners accepted the plan of God. That is why Jesus said that the least in the kingdom of God is greater than John.