The outward act of the Lord's Supper does not give grace...

We showed in our Confession our belief that the Lord's Supper does not give grace by the outward act (ex opera operato) and that, when applied on behalf of others, alive or dead, it does not merit for them the forgiveness of sins, guilt, or punishment by the outward act.  This position is supported by a clear and firm proof.  It is impossible to receive the forgiveness of our sins because of our own work by the outward act.  The terrors of sin and death must be overcome through faith when we comfort our hearts with the knowledge of Christ and believe that for His sake we are forgiven and that His merits and righteousness are granted to us, "since we have been justified by faith, we have peace" (Romans 5:1). These things are so sure and so firm that they can stand against the gates of hell.
~BOC, AP, XXIV (XII)11-12

Those who condemn the Word of Absolution in favor of their own words are enthusiasts...

All this is the old devil and old serpent, who also turned Adam and Even into enthusiasts.  He led them away from God's outward Word to spiritualizing and self-pride.  And yet, he did this through other outward words.  In the same way, our enthusiasts today condemn the outward Word.  Yet they themselves are not silent.  They fill the world with their babbling and writings, as if the Spirit could not come through the apostles's writings and spoken Word, but has to come through their writings and words.  Why don't they leave out their own sermons and writings and let the Spirit Himself come to people without their writings before them, as they boast that He has come into them without the preaching of the Scriptures?
~BOC, SA, III, VIII, 5-6

Baptism, as with the entire Gospel, is an outward, verbal preaching...

Now these "new spirits" are so crazy that they separate faith and the object to which faith clings and is bound, even if it is something outward.  Yes, it shall and must be something outward, so that it may be grasped by our senses and understood, and by them be brought into the heart.  For indeed, the entire Gospel is an outward, verbal preaching.  In short, what God does and works in us He intends to work through such outward ordinances.  Therefore, wherever He speaks--indeed, no matter what direction or by whatever means He speaks--faith must look there.  It must hold to that object.  Now here we have the words "Whoever believes and is baptized will be saved" (Mark 16:16).  What else can these words refer to but Baptism, that is, to the water included in God's ordinance?  Therefore, it makes sense that whoever rejects Baptism rejects God's Word, faith, and Christ, who directs us to Baptism and binds us to Baptism.
~BOC, LC, IV, 30-31

Baptism gives faith the outward thing upon which it stands and rests...

Our would-be "wise spirits" assert that faith alone saves, and that works and outward things do nothing.  We answer, "It is true, indeed, that nothing in us is of any use but faith, as we shall hear still further."  But these blind guides are unwilling to see this:  faith must have something that it believes, that is, of which it takes hold and upon which it stands and rests.  So faith clings to the water and believes in Baptism, there is pure salvation and life.  This is not through the water (as we have stated well enough), but through the fact that it is embodied in God's Word and institution, and that God's name abides in it.  Now, if I believe this, what else is it than believing in God as the One who has given and planted His Word into this ordinance and offers to us this outward thing by which we may gain such a treasure?
~BOC, LC, IV, 28-29