Mark 1:4

John came, who baptized in the wilderness and preached the baptism of repentance unto remission of sins. And there went out unto him all the country of Judaea, and all they of Jerusalem; and they were baptized of him in the river Jordan, confessing their sins.

The wilderness ... That John was indeed the Elijah whose voice would cry "in the wilderness" is evident in the fact that, of all the great preachers in history, only one chose a wilderness as the scene of his ministry.

Baptism of repentance unto remission of sins ... John's baptism was a heavenly device for gathering together out of the nation of Israel a prepared people to receive and adore the Messiah. This baptism was of God, and those who rejected it rejected God's message (Luke 7:30). In God's plan of redemption, a new birth was the essential prerequisite, a birth of water and of the Spirit (John 3:5). The birth of water (John's baptism) was available to men in the preaching of the herald; and, for those who accepted it, the birth from the Spirit would follow, in time, when it was made possible through the Saviour's death. The fact that those who rejected John's baptism did not follow Christ and did not receive the Holy Spirit is parallel with the truth that persons today who refuse the baptism Jesus commanded cannot receive the Spirit.

All the country ... all they ... The success of John the Baptist was sensational and extensive. Great crowds and widespread popularity marked his efforts. The great wilderness preacher aroused the nation from its slumber, arrested the attention of that whole generation, and created excitement throughout the country. Even the Pharisees at first accepted him and "were willing to rejoice for a season in his light" (John 5:35). This great popularity, however, did not last. As Ryle said:

The vast majority, in all probability, died in their sins. Let us remember this when we see a crowded church. It is not enough to hear and admire popular preachers. It is no proof of our conversion that we always worship in a place where there is a crowd. Let us take care that we hear the voice of Christ and follow him.[2]