Mark opens his Gospel with these words. “The beginning of the gospel of Jesus Christ, the Son of God.” (Mark 1:1 ESV)
Verses 2-3, interestingly enough, follows right after verse 1. In those verses we have some Old Testament quotes referring to John Baptist. Now, regardless if you believe that verse 1 is a title to Mark’s Gospel, it is interesting that he sees the Gospel as beginning with these quotes. By starting with these Old Testament quotes, Mark demonstrates two truths.
First, the Gospel is not secondary to the meaning of the Old Testament, but rather, the Gospel is the fulfillment of the Old Testament. This what Jesus taught in the Sermon on the Mount (Matthew 5:17), what Peter preached at Pentecost (Acts 2:14-36), and part of Paul’s definition of the Gospel (1 Corinthians 15:1-4). Mark begins his ‘Gospel’ by pointing us to this truth, that everything that happened during the life and ministry of Jesus had been foretold. The Gospel is according to the (Old Testament) Scriptures.
Secondly, Mark points us to the truth that God’s Word does not return void. Just as it had been foretold through the prophets that there would be a forerunner of the Messiah, those prophecies were fulfilled to the letter. However, these prophecies were not made in order to point us to John, but they were signs along the way pointing us to Christ. In showing us who the forerunner of the Messiah is, they show us the Messiah. So just as God had promised, the Messiah came (Genesis 3:15), lived (Isaiah 53:2-3), died (Isaiah 53:7), rose again , ascended to Heaven, and is pleading our case before the Father(Isaiah 53:12).