It is written in Isaiah the prophet: "I will send my messenger ahead of you, who will prepare your way" - a voice of one calling in the desert, 'Prepare the way for the Lord, make straight paths for him.'"
From Mark's point of view, the story of Jesus began with the ministry of John the Baptist. But even as Mark begins to tell briefly John's part in setting the stage for the earthly ministry of Jesus, the Gospel writer cannot refrain from making mention of the fact that the message of salvation in Christ Jesus was conceived in the heart of God long, long before the voice of the forerunner was heard crying in the wilderness.
This Mark does by referring to two Old Testament passages concerning the coming Lord:
In Malachi 3:1 - "See, I will send my messenger, who will prepare the way before me. Then suddenly the Lord you are seeking will come to his temple; the messenger of the covenant, whom you desire, will come," says the LORD Almighty.
In Isaiah 40:3 - A voice of one calling: "In the desert prepare the way for the LORD; make straight in the wilderness a highway for our God.
In those brief words, Mark identifies Jesus as the promised Deliverer and John the Baptist as the promised forerunner. In effect, Mark is assenting to the truth that was later to be more clearly expressed by the writer of the Letter to the Hebrews when he said: "In the past God spoke to our forefathers through the prophets, at many times and in various ways, but in these last days he has spoken to us by his Son, whom he appointed heir of all things, and through whom he made the universe." (Hebrews 1:1-2)
From the historical point of view, the message of salvation began with the ministry and message of Jesus Christ. Yet, in the purpose of God, it began the very moment that sin entered into the world to separate man from God - and, indeed, prior to that... for, as John puts it in the book of Revelation, Jesus Christ is the Lamb of God, "that was slain from the creation of the world" (Revelation 13:8). The scarlet thread of God's redemptive purpose runs throughout the entire Old Testament. Jesus came in human form to fulfill God's promises to man.