Of Justification, XI:3

Christ, by His obedience and death, did fully discharge the debt of all those that are thus justified, and did make a proper, real, and full satisfaction to His Father's justice in their behalf. Yet, in as much as He was given by the Father for them; and His obedience and satisfaction accepted in their stead; and both, freely, not for any thing in them; their justification is only of free grace; that both the exact justice, and rich grace of God might be glorified in the justification of sinners.

The Confession here asserts the substitutionary ("in their behalf") satisfaction theory of Christ's atonement. That is no minor fact for us in the early 21st century to notice given the current attack upon that theory. But the Confession also doesn't spend a lot of time on the concept, instead being more concerned to point out that this is all of grace.

Christ, the sacrificial Lamb of God, was given by the Father on behalf of believers; the Father accepted his "obedience and satisfaction" in place of theirs. Both the giving and the accepting were/are entirely of grace. God has never been under any obligation to save sinners. That he does so through Christ is entirely gracious and of his free will. The purpose or end of this was not chiefly that sinners would be saved (think of it as a happy secondary effect) but that God would be praised for both his glorious grace and glorious justice.

This may not make a man happy--indeed, the natural man will not understand it and will typically mock, scoff, and rage against it. It is contrary to much of what passes for the "gospel" in the contemporary West, our thinking even in the church being so man-centered that we vainly imagine that God has orchestrated all this primarily for our benefit.

Tomorrow: The decree and application of justification.