“I say to you, Among those who are born of women there is none greater than John, yet he who is but little (or ‘least') within the Kingly Rule of God is greater than he.”
So among those born of women there is no greater than John the Baptiser. But now in Jesus what John pointed to is fulfilled (as He has pointed out to John previously in Luke 7:22-23). The Kingly Rule of God is here in the King, and those who now enter it have a standing higher even than that of John. They are not only born of the Spirit, they are directly servants of the King Who is present among His people, a privilege that John has never had (significantly there was the indication here that John would never leave prison. His task was done). It is clear from this the high status and position that Jesus is claiming for Himself. The greatest of all men has now been superseded by the Greater, by the King, by ‘Christ the Lord' (Luke 2:11).
As the New Testament tells us elsewhere, this was the day that the prophets and righteous men of past ages had longed for. They had longed to see what these people saw, and to hear what they heard (Matthew 13:17; 1 Peter 1:10-12). And now it was here. And John had to sink into the background because the One was here to Whom all the ages had pointed.
Others see ‘he who is least' as a reference to Jesus Himself, thus stressing that He is here as the King under God, because made man least in the Kingdom of Heaven. ‘Least' then contrasts here with ‘greater'. John may be great among men, but Jesus is under the Kingly Rule of God, where the least is greater than the greatest on earth. Or perhaps He had in mind His Apostles (Luke 22:26).
‘There is none greater than John.' John is described as the greatest of all men who have been born into the world. Furthermore as ‘more than a prophet' he is the greatest of the prophets. But his greatness becomes insignificant in comparison with things to do with Heaven. These last probably include the thought of the new birth from above (John 3:5-6) by which those who are born of the Spirit enter the Kingly Rule of God (John 3:5) having been made partakers of a heavenly/divine nature (2 Peter 1:4), but it cannot just mean that for we must not deny to John the birth of the Spirit. More probably the thought is of the outpouring of the Holy Spirit which will result in signs and wonders. (John did no miracle - John 10:41).
Does this then mean that John could not enter under the Kingly Rule of God? That is certainly not the idea. But what he cannot do is enter it on earth as a direct servant of the King. Jesus had not set Himself up as King until John was imprisoned (Luke 2:20; Mark 1:14). Thereby his ministry ceased and Jesus' independent ministry began in the proclaiming of the Kingly Rule of God (Mark 1:15). Those who now enjoy a position under Him are thus greater on earth than John for they are in the direct service of the King. The prophet has fulfilled his great ministry. Now the Greater than he reigns, along with His Apostles.