Of the many admonitions addressed by John to the multitudes, Luke mentions only a few. But what he mentions is typical and representative of the general trend of his preaching. In these words we hear John addressing the people in fearless and pointed terms – drawing their attention to their sins and calling them to true repentance. He warns and threatens them as he announces the approaching judgment on those who refuse to turn to God. He does not even hesitate to address them (according to Mathew 3:7 it was especially the Pharisees and Sadducees) as a “brood of vipers.” In these words he draws attention to their tortuous behavior – they live in self-satisfaction and sin and now they desire, without true conversion and by a merely external participation in the baptism, to protect themselves against the impending judgment. He summons the people to whole-hearted repentance, after which they must have themselves baptized as an outward sign of their acknowledgment of their spiritual impurity, so that the baptism may be to them a sign and seal of the forgiveness granted by God to the meek… He warns them not to rely on their natural descent from Abraham, but to see to it that their repentance is genuine… In his promises to Abraham, John declares, God is not bound to his descendants in the flesh: unless they are true children of Abraham in a spiritual sense, the wrath will come upon them and God will show His salvation among other nations to true, spiritual children of Abraham.
There must be no postponement of repentance on the part of his hearers, for the axe is already being laid to the root of the trees – the judgment is on the point of being executed on those who remain unrepentant.
Alarmed at his urgent words, the multitude ask what they shall do. They thought that they had to do something special, but John replies that they must do what lies to their hand and carry out the well-known demands of God – show true neighborly love.
Even “publicans,” Jews who, as agents of Caesar or Herod, collected customs duties and were hated and despised by the people, came to John asking what they should do to escape the wrath to come. And again John replies that they must live lives of neighborly love in their particular profession. He does not demand that they should give it up, but that they should show the genuineness of their repentance by never abusing their position…
He also does not forbid the soldiers…to be soldiers, but makes the inexorable demand that they, too, should exercise neighborly love in their particular circumstances…
Thus far Luke has shown how John through his earnest and urgent appeal for whole-hearted and practical repentance was engaged in preparing the people for the coming of the Messiah. He now relates how John, when the people began to wonder whether he was the Messiah, expressly and unconditionally placed himself in the background and pointed to Christ, the One who was coming, as the promised Redeemer.
John then points out that, no matter how important and necessary his preparatory work and baptismal ministration are, they are of quite subordinate value in comparison with the work of the coming Messiah. He can only administer the outward baptism, but Christ will bring about the inward purification and renewal. He will administer the true baptism (with the Holy Ghost and with fire) – a baptism which gives inwardly what is outwardly symbolized by by the baptism in water. Just as fire consumes what is destructible and thus works in a purifying and cleansing manner, so the Messiah will through the Holy Ghost consume sin and the sinners in so far as they cling to sin…
The coming of the Redeemer will not mean salvation for all – He will sift and separate men like one who with a pitchfork or winnowing-fan tosses in the air the already threshed-out wheat on the threshing-floor so that the chaff may be separated from the wheat, the chaff being blown away while the wheat falls on the floor. So those receiving baptism must see that their repentance is genuine so that they may be truly saved. While most of the Jews of that time thought that the Messiah was going to visit only the heathen with His judgment and that they themselves would be privileged above all others, John declares plainly that judgment will overtake all who are not prepared for His coming through a true change of heart.
[18 “And with many other words, John exhorted the people and preached the good news unto them.”]
This verse proves that Luke included in his Gospel only a few typical pronouncements of John. Although John with so poignant earnestness called the attention of the Jews to their sins and to the impending judgment, Luke nevertheless declares that he “preached good tiding unto the people.” John’s preaching is thus a true proclamation of the Gospel because he announces that the Messiah is coming who, while He will visit the unrepentant with His judgment, brings forgiveness of sins and inward renewal and purification through the Spirit to all who truly turn to God and sincerely await His coming and take refuge in Him.