The following are quotations from Luther's 8-volume Genesis Commentary (American
  Edition of Luther's Works published by Fortress Press and Concording
  Publishing House) where he questions the salvation of Anabaptists, today's
  Baptists, and Sacramentarians, those who reject the physical presence of
  Christ's Body and Blood in the Lord's Supper for the forgiveness of sins.
  "Thus the Anabaptists, the Sacramentarians, and the papists are all
  idolaters-not because they worship stones and pieces of wood, but because they
  give up the Word and worship their own thoughts." LW1:149
  "Nevertheless, I do not deny that even after Methuselah's death Noah
  heard God speaking. God speaks with men in a twofold way: in the first place
  and ordinarily, through the public ministry, that is, through parents and the
  teachers of the church; in the second place, through inner revelation or
  through the Holy Spirit. This latter method, however, He is wont to employ
  only in special situations and very rarely. It is profitable to be aware of
  this, so that we may not emulate the fanatics, who disregard the Word and
  expect new revelations. It is this idea that gives rise to the misguided
  spirits who later on bring confusion to the world by their dreams, as the
  example of the Anabaptists proves.' LW2:83
  "All the fanatical spirits follow this procedure of Satan. Thus Arius
  raises the question: "Do you believe that Christ is God, inasmuch as He
  clearly states (John 14:28): The Father is greater than I'?" Likewise the
  Sacramentarians: "Do you believe that the bread is the body of Christ,
  and the wine the blood of Christ?" LW1:152
  "We have Christ's clear word about the Lord's Supper, where He says
  concerning the bread: "This is My body which is given for you," and
  concerning the cup: "This is the cup of the New Testament in My
  blood." Therefore when the fanatics depart from faith in these words and
  discuss how these things can be so, they gradually get to the point where they
  simply deny this word of Christ and attack it, just as happened to Eve in this
  passage." LW1:157
  "Moreover, by his addition-"And the earth was filled with
  violence"-he indicates that this is the unvarying sequence of events:
  after the Word has been lost, and faith has ceased to exist, and tradition and
  (Greek text), as Paul calls them (Col. 2:23), flourish in place of the true
  forms of worship, acts of violence and a shameful life follow." LW2:59-60
  "Thus at the beginning of the restoration of the Gospel,32 Münzer,
  Carlstadt, and the Sacramentarians arose. They abandoned the Gospel, which had
  been given through the Holy Spirit from heaven, and were on the lookout for
  extraordinary illuminations. Some arrived at such a degree of folly that they
  boasted of hearing the voice of God speaking in heaven." LW4:125
  'If your dream differs from what the Word itself states, you must remember
  that it is false and vain. But this dream of Jacob is in very beautiful
  agreement with the divine Word which he hears being sent down from heaven:
  "I am the Lord, etc." Therefore the godless err in their
  interpretation and understanding of dreams, just as they talk nonsense when
  they explain signs and prodigies; for they neither observe nor have the Word.
  This is what happened to the Anabaptists at Münster, who had seen a bow in
  the clouds and next to it a bloody hand." LW5:239
  "But it is very troublesome that my wisdom is only passive and that I
  am ordered to mortify and kill it. Indeed, on this account many have fallen
  horribly, since they could not bear this mortification. Thus the
  Sacramentarians teach God most prettily: "How could Christ's body be in
  the bread and wine when Christ has ascended into heaven?" For they think
  as follows: "Because I cannot comprehend the presence of the body and
  blood in the Lord's Supper, I shall prescribe to God some way in which He can
  be present." LW7:104
  "But one of these days it will be evident what our heretics and
  fanatics will dare. For today both the Anabaptists and the Sacramentarians
  despise the Word and neglect the doctrine of faith. Meanwhile they manifest
  the greatest show of devotion and respectability. I hear that there is very
  strict discipline among the Swiss.35 They do not play, do not gormandize, and
  do not give themselves up to luxury in clothing, in feasts, etc. This is their
  religion, and they are proud of it. They boast that they excel us by far. But
  where is the Word? "The body of Christ," they say, "is in
  heaven; but the bread is bread, and the wine is wine." They believe
  nothing but have fallen away from the Word and faith." LW8:133
  "Thus we-not only when we pray, but also when we baptize, absolve,
  have been absolved, and go to the Lord's Supper, yes, even at the reading of
  the promises or the text of the Gospel-should bend our knees or at least stand
  as a sign of our adoration or reverence and gratitude. Accordingly, even if
  nothing else were offered in the Lord's Supper than bread and wine, as the
  Sacramentarians blasphemously assert, nevertheless the promise and God's Word
  are there, and the Holy Spirit works through the Word at the Supper. For this
  reason we should approach it with reverence. But how much more fitting it is
  for this to be done when we believe that the true body and the true blood are
  present with the Word! " LW8:144