Mark 1:4

John did baptize in the wilderness, and preach the baptism of repentance for the remission of sins.

Two of the prophets of olden times had distinctly described the person and the work of John the Baptist, and the evangelist combines their prophecies for the purpose of brevity. The first prophecy, Malachi 3:1, is one in which the God of Israel promises to send His personal messenger before the Messiah. And this messenger, by the message which should be imparted to him and which he was to proclaim before the people of the nation, had the purpose, the object, of preparing the way for the Messiah. A thorough preparation of the way was necessary and should be accomplished by the message entrusted to the herald. In the second prophecy, Isaiah 40:3, the distinctive contents of the message are given. It is a voice, preaching, which is heard; not a soft, gentle, and obscure whispering as of one not at all sure of his ground, and not filled with the conviction of the divinity of his message, but a loud calling, to awaken sinners from their sleep of security and indifference. A distinguishing feature: It would be heard, not in the midst of the capital or in the halls of the learned of the people, but out in the wilderness, far from the abodes of men. Simple, but impressive its import: Make ready the way of the Lord; make smooth the highway before Him. It is a spiritual coming of which the prophet speaks; it is the heart and mind that must be prepared for the coming of this Lord, who intends to establish His throne in the hearts of the believers. Only the penitent humble sinners are admitted into this Kingdom. The rocks of self-righteousness, of pride and self-conceit, of a religion of works, will not permit the King to enter into the hearts. These must be removed so thoroughly that not a trace is left behind. That is the sum of the herald's preaching, of his work in preparation for Christ's coming. In fulfilling this prophecy, John the Baptist was out in the wilderness; he appeared out in the arid regions between Jerusalem and the Dead Sea, where the hills slope downward to the Jordan; he began his ministry as one that baptized. He made use of this rite, by God's express command, to emphasize still more strongly his preaching. For his was a proclamation of the baptism of repentance for the remission of sins. It was not a mere proselyte baptism, nor was it altogether identical with that of Jesus and the New Testament sacrament. Those that really repented of their sins received remission, forgiveness of their sins, and this remission was sealed unto them by the baptism which was administered unto them by John.