“What did Jesus mean when He said the least in the kingdom was greater than John?”
“…Among them that are born of women there hath not risen a greater than John the Baptist: notwithstanding he that is least in the kingdom of heaven is greater than he” (Matt. 11:11).
Some feel that the Lord was speaking of Paul, since the apostle uses the word “least” to describe himself twice (1 Cor. 15:9; Eph. 3:8). However, “the kingdom of heaven” of which the Lord spoke was the kingdom that will one day be established on earth for the redeemed in Israel, and Paul was never a part of that kingdom, nor will he ever be.
In that kingdom, all the redeemed will be filled with God’s Spirit, who will “cause” them to walk in His statutes (Ezek. 36:27). Because of this, the least member of that kingdom will be incapable of sinning, and so will exceed the righteousness of even a man as holy as John. Speaking of the kingdom, the prophet declared,
“…he that is feeble among them at that day shall be as David; and the house of David shall be as God, as the angel of the Lord before them” (Zech. 12:8). source