In traditional systematics, distinct aspects of the work of salvation are often attributed to each person of the Trinity. The Father chooses, the Son redeems by his blood and the Spirit applies the work of salvation. But this neat pattern does not reflect the witness of Scripture. Each aspect of salvation is thoroughly trinitarian. The Father chose us in Christ through sanctification of the Spirit. In the incarnation the Father sent the Son into the world as man by the power of the Holy Spirit. At the cross, the Son offered himself to God through the eternal Spirit. In terms of the application of redemption, God made us alive together with Christ when we were born again by the Holy Spirit. Eschatologically, we shall be raised to life and glory by the Spirit of him who raised Jesus from the dead. Systematics should reflect the trinitarian concerns of Scripture when seeking to construct a truly biblical account of soteriology.
Professor Donald Macleod's reminder is both insightful and timely. I'm thinking of today's criticism against Penal Substitutionary Atonement (PSA) that is often held out - that what happened on the cross was 'cosmic child abuse' as Jesus the inncocent Son was being punished for no wrong of his; that such an act, far from showing God's justice, actually smacks of injustice since an innocent party pays for the wrongdoing of another party etc. What lies at the heart of the failure of these criticisms is that they have not taken into account that it is the One God who is Trinity that has carried out the atonement. God the Father and Jesus the Son are not two separate parties (and the Spirit often goes missing in such an account of the atonement); but that Father, Son and Spirit together form one party in the act of the atonement. In the words of Karl Barth, "God entered into His own wrath." God (in the person of the Father) deals with his own wrath and right response to sin by God (in the person of the Son) offering Himself as an act of atonement on the cross through God (in the person of the Spirit) perfecting that work of obedience and the bond of unity within the Godhead (Heb 9:14). Tis the mystery! Seen in this light, the cross actually provides an insight into the Trinitarian relationships within the Godhead, and such is the basis of the approach taken in Jurgen Moltmann's classic The Crucified God.
(For the full article by Professor Donald Macleod, refer to http://exiledpreacher.blogspot.com/2009/03/donald-macleod-on-practical.html)