In studying Isaiah 40 for this week’s message, I found this brilliant passage in one of my commentaries on Isaiah. In this section, Dr. Child’s goes to great lengths to show the profound connections between what is known as first Isaiah (ch. 1-39) and second Isaiah (ch. 40-55). In doing so, he also picks up themes that find their fulfillment in Christ. I always find this sort of thing fascinating as I live in a society that does not seem to know what to do with the Old Testament and what it says about God.
When John the Baptist linked the appearance of Jesus with the prophet’s call to ‘prepare the way of the Lord,’ he was not making a mechanical connection with an ancient prediction of Isaiah. Rather, the reality of God’s salvation was manifest in Jesus Christ in such a way that his advent provided a perfect morphological fit according to its redemptive substance with the Old Testament promise. In a word, the salvific significance of Jesus Christ was understood in the light of the Old Testament prophecy, while, conversely, the Old Testament promise gained its true meaning from the revelation of the Christ in the fullness of God’s time.
Brevard Childs commentary on Isaiah in the Old Testament Library series (p.303)