Having come across bits of discussion on the subject of sacrifice and sacrament, prayer and proclamation, it seems to me that we try vainly to neatly tie up things into boxes as if they did not have other dimensions and relationships. Lutherans, of all denominations, ought to be comfortable with the same words spoken with different hearers in mind and for different purpose.
A million years ago when the Eucharistic Prayer was the hot topic there were those who went to great lengths to insist that the Words of Institution could not be placed within a context of a prayer (even though they have been since the earliest days of Christianity and were only unhinged from the prayer at the time of the Reformation). Part of the argument was that prayer and proclamation are two vastly different things (which they are) and could not possibly be together. At the time I wondered about this and have read and conversed with some folks along the way who wondered about this as well.
To speak simplistically, Rome sees the Words of Institution as words addressed to the Father, the prayer of the Church heeding the bidding of Christ and presenting to the Father the sacrifice Christ once offered of His body and blood. To speak simplistically again, generally Protestants see the Words of Institution as words addressed to the people, the proclamation of what Christ did to rekindle their memory of His atonement and direct them to the action that formally remembers what He did by eating a bit of bread and drinking a bit of grape juice in His memory.
Again, to speak simplistically, Lutherans see it both ways. We deny that that the Word is some magical formula that once spoken incants the presence of Christ's body and blood in bread and wine the way poor old Aunt Clara got her spells messed up and ended up incanting the unintended. We insist that the priest is not the effector of the presence of Christ, who is given in ordination the secret power to unlock heaven and bring Christ's body and blood to the earth. What we believe is that the Words of Institution are prayer addressed to God, the prayer of the Church who does Christ's bidding, speaks His Word, and calls upon God to fulfill His promise and make this bread to be Christ's body and this cup His blood. But at that very same time, the Words of Institution are proclamation to the people. Because the Word of God is efficacious and does what it says and the people have assembled in the name of Jesus to receive what He has promised, they can have every confidence that the Word will accomplish what it proclaims and this bread becomes the body of Christ (without destroying the bread) and this wine His blood (without destroying the wine). The same words, two different hearers, and different purpose.
In the same words we find both prayer addressed to God and proclamation addressed to the assembly. They are not in conflict. Without turning this into an academic treatise, we can find ample sources in the fathers and in the Lutheran theologians to support both of these (I think among contemporary theologians Dr. David Scaer would come down along these lines). One does not preclude the other, contra Oliver K. Olson and Gerhard Krodel among others who insist that the two may not occupy the same space.
When it comes to the role of the Spirit in the Eucharistic mystery, we find ourselves in a similar spot. While the East would point to the epiclesis as the "consecratory" element of the Eucharistic Prayer, the West (ala Ambrose) have pointed to the Words of Institution. Where the East sees the key in the prayer addressed to the Spirit to do what the words proclaim, the West has seen the key in the canon of the mass and in particular the words of Christ's testament.
For Lutherans the Spirit always works through the Word (written, spoken, or visible). Therefore, the words of Christ always include the agency and effect of the Spirit. The Spirit is at work in the presence of Christ's body and blood in the Sacrament because the Spirit works in and through the Word. The Spirit is partner in this Word as He is always partner in the work of the Word (such as creation when the Word speaks and the Spirit effects what the Word proclaims -- working together). In the end this is surely very Trinitarian.
Finally a few thoughts on sacrifice and sacrament. Jack Kilcrease has put it well in his blog comment. It is a matter of perspective. For God the Mass is a sacrifice -- can God look upon the body and blood of His Son without looking through the once for all sacrificial death on the cross to view that body and blood? We do not sacrifice Christ nor do we present again the one, all sufficient sacrifice. But we do remind God of that one and only way through which we may stand before Him and serve Him as His priestly people. We do that by holding up the body and blood of Christ, of His sacrificial death for us and for our salvation. This is not something we do for intent as it is the very natural way God sees and responds to what we are doing in heeding Christ's testament and "do this in remembrance of Me."
But this is certainly not the primary purpose of either the Words of Institution or the Sacrament. More important than this is the sacramental purpose. This bread and this blood are for the faithful eating and drinking of Christ's people, as He intends, for the forgiveness of their sins, for the strengthening of their faith, and for the nourishment of their bodies and souls to eternal life. For us the Mass is sacrament. The promise is fulfilled not only in the Words spoken over bread and wine to set them apart according to Christ's command but so that the faithful may eat and drink the body and blood of Christ hidden in the bread and wine. We proclaim the eternal event of Christ's sacrifice to the Father even as we proclaim it and receive it in the eating and drinking of the Sacrament as the people of God, the body of Christ the Church.
Again, you can find ample quotes in Luther for this as well as the fathers and the Lutheran theologians (again, I refer to Dr. David Scaer here). My point in all of this is that some try so very hard to box theology up into standard sizes and forms, to resolve all conflicts and loose ends, to turn the questions into simple black and white issues. The genius of Lutheran theology is that we allow the Word to be the Word. We accept the seeming contradictions without trying to clean up God's mess for Him. We are servants of the Word and not its masters. We see how the same words, speak to different hearers (God and man), for different purpose (prayer and proclamation, sacrifice and sacrament).
Well, I am sure this post will stir up something... Oh, well, every now and then we need to clean out the cobwebs...