One notable feature of Mark's Gospel is his portrayal of Jesus as the servant of God. The theological center of this theme is found in Mark 10:45: "For even the Son of Man did not come to be served, but to serve, and to give his life as a ransom for many." Although Jesus was Israel's promised King and Messiah, He did not come to reign but to serve by offering His life as a ransom. This New Testament word speaks of exchange. In other Greek writings, it refers to the price paid to buy back a prisoner of war or a slave. The prophet Isaiah predicted that Israel's Messiah would come as a suffering servant. According to Isaiah 53:10 it was the Lord's will to make Christ suffer because this suffering was "an offering for sin."
Two important theological terms are used to explain what it means that Jesus gave His life as a ransom, penal and substitutionary. To say that Jesus’ suffering was penal means His suffering was neither an accident nor a tragedy. He voluntarily gave His life to satisfy our deserved punishment. He shed His blood to pay the ransom God’s justice demands for our sin. When we describe His suffering as substitutionary, we emphasize that Jesus did not do this for His own sake but for ours. Those for whom He died have been buried and are risen with Him (Rom. 6:4).
God is both the initiator and the recipient of this spiritual transaction, but we are the beneficiaries. God sent His Son into the world (John 5:36). He accepted Christ’s suffering as a satisfactory payment for our sin. Yet the reward is given to us. Paul expresses the essence of Christ’s substitutionary work on our behalf in 2 Corinthians 5:21: “God made him who had no sin to be sin for us, so that in him we might become the righteousness of God.” In Mark 10:45 Jesus points to His suffering as an example. But before we can serve we must be served. When we trust in Christ, we exchange our sin for His righteousness. Only then are we fit to serve Him.
To learn about the penal and substitutionary nature of Christ’s work, read Pierced for Our Transgressions: Rediscovering the Glory of Penal Substitution by Steve Jeffery, Michae Ovey, and Andrew Sach (Crossway).