Originally Posted by
togre
As a substitute. The entire sacrificial system of the Old Testament was God teaching and preparing his people. Teaching them that sin required death, a payment in blood. Teaching them that a substitution is permitted so that God can punish sin with justice and yet forgive his people in mercy.
If your work had a strict set of rules they would require behavior A from you and prescribe punishment B in case of failure. Christ, as a Substitute, provided the required behavior (sinlessness) and did so in our place. Christ, as a substitute, endured the prescribed punishment (hell) and did so in our place. God the Father was pleased, indeed, the author of this plan.