John the Baptist – even though he appears in the four gospels – was the last of the Old Testament prophets. Here is his description of the coming Messiah, “As for me, I baptize you in water for repentance, but He who is coming after me is mightier than I, and I am not even fit to remove His sandals. He Himself will baptize you with the Holy Spirit and fire. And His winnowing fork is in His hand, and He will thoroughly clean His threshing floor, and He will gather His wheat into the barn, but He will burn up the chaff with unquenchable fire.” (Matthew 3:11-12).
Notice the imagery used by John the Baptist. He is clearly a prophet in the Old Testament mold. In fact, I think he is hoping to see some old covenant judgment action on Jesus’ part with words like “winnowing hook … thoroughly clean His threshing floor … burn up the chaff with unquenchable fire.” Of course, judgment was not the purpose of Jesus’ first coming.
But John is aware that something is changing. Later, when Jesus begins His public ministry, crowds begin to follow Him, and John’s influence seems to wane. Into this setting, John says, “He must increase, but I must decrease” (John 3:30).
I think what John is saying here is much more than just a comment of personal comparison with Jesus. John is making a prophetic point. It is as if John is saying, “I, as a representative of the old covenant, am fading away. Jesus and His announcement of a new covenant, a new way of relating to God, must come to the forefront.”
The apostle Paul expands on this idea in II Corinthians 3. In the context of describing the old and new covenants, Paul writes, “For indeed what had glory [old covenant], in this case has no glory because of the glory that surpasses it [new covenant]. For if that which fades away [old covenant] was with glory, much more that which remains [new covenant] is in glory” (II Corinthians 3:10-11).
The old covenant must fade away. The message of John the Baptist must decrease. The message of Jesus must increase. The coming of the new covenant is here.