God’s perfectly righteous character (Deut. 32:4) means that our Creator can by no means look the other way when it comes to sin. If a just judge on an earthly level will hold people accountable for breaking the law, how much more will the holy Judge of all do so? For sinners, this is a terrifying prospect indeed. Thankfully, Scripture reveals to us that God is merciful as well as just. He has made it so that He can forgive us without compromising His justice by allowing a substitute to bear the punishment for sin in our place.
This notion of vicarious substitution weaves its way throughout the Bible and is present from the very beginning chapters of Genesis. For instance, many Christian theologians have seen the principle of substitution in God’s killing an animal to clothe Adam and Eve after the fall (Gen. 3:21). The principle that the Lord will accept the death of a substitute in place of the death of a sinner is perhaps even more clear in God’s substitution of a ram for Isaac once Abraham passed his great test of faith (22:1–19). And of course, vicarious substitution is at the heart of the old covenant sacrificial system, wherein bulls, oxen, goats, sheep, and doves were offered up by the priests to atone for the sin of the Israelites.
Vicarious substitution involves not only a death in our place but also a life in our place. Reformed theologians have been clear that the death of Christ, while necessary, would be insufficient to save us apart from the righteous life of Jesus. The shedding of Christ’s blood takes away our sin (John 1:29), but the death of Jesus in itself can only wipe our slate clean of wickedness. Apart from His life of perfect obedience, the atonement would merely return us to a state of probation. We would lack the record of obedience that is needed if we are to live forever. Eternal life comes only to those who keep God’s law positively, not merely to those who have no record of sin (Rom. 5:12–21).
Thus, Christ had to live for us in addition to dying for us. He had to keep the law of God on our behalf. We see this taught in many ways in the New Testament. In today’s passage, for instance, Jesus says that He must be baptized “to fulfill all righteousness” (Matt. 3:15). Through John the Baptist, God commanded His people to be baptized. This command had to be kept if Jesus were to live a perfectly righteous life, which is imputed to us—put on our accounts before God—when we believe in Christ.