In The One Mediator, the Saints, and Mary, Lutheran scholar Eric W. Gritsch, who was a major translator in the English set, Luther’s Works, observed that “Luther affirmed Mary’s assumption into heaven but did not consider it to be of benefit to others or accomplished in any special way.”

In the same book, 12 Lutheran and 10 Catholic scholars participated. Their “Common Statement” (a sort of creed-like formulation agreed upon by all) yielded some very interesting conclusions indeed:

• “Luther preached on the Assumption. … There were early Lutheran pastors who affirmed the Assumption as both evangelical and Lutheran.”
• “From the Lutheran side, one may recall the honor and devotion paid to the Mother of God by Luther himself, including his own attitude to the Immaculate Conception and the Assumption, which he accepted in some form.”

Luther stated in a sermon in 1522:

There can be no doubt that the Virgin Mary is in heaven. How it happened we do not know. And since the Holy Spirit has told us nothing about it, we can make of it no article of faith.

Luther signed an Aug. 19, 1527, letter to Georg Spalatin in the following (very “un-Protestant”) manner:

Yours, Monday after the Assumption of Mary, 1527. Martin Luther.

In his 1532 sermon, Luther stated:

We, however, even if she has already gone to heaven, cannot enjoy her ascension, and should not for that reason call to her or to take comfort in her intercession.

William Cole cites Luther as saying in 1544:

The feast of the Assumption is totally papist, full of idolatry and without foundation in the Scriptures. But we, even though Mary has gone to heaven, should not bother how she went there. We will not invoke her as our special advocate as the Pope teaches. The Pope takes away the honor due to the Ascension of our Lord, Christ, with the result that he has made the mother like her Son in all things.

Even this doesn’t particular quotation necessarily require that Luther himself gave up all belief in Mary’s Assumption, since he was discussing not the thing itself, but how the feast celebrating it was conducted in the Catholic Church (thus, he referred to invoking her, etc., as he also did in 1532, which has nothing directly to do with the doctrine itself). Cole observed:

For Luther the Assumption seems not to be so much a matter of doubt as of little importance and this is perhaps the reason  … that Luther did not pronounce clearly on the subject, but was content simply to affirm it. …

In summary, we can see that if the Feast is rejected, it is for reasons extraneous to the fact itself, which Luther never denied. Essentially, as Luther himself said in the same sermon the reason he does not celebrate it, ‘although she has gone to heaven’ is that he sees it as a source of justifying invocation to Mary.

“Affirm” means holding a belief, and Cole also states that Luther “never denied” it. The well-known Luther scholar Eric Gritsch also thought he believed in Mary’s Assumption, as did the 12 Lutheran scholars in the ecumenical book mentioned above. None of them even claimed that he stopped doing so. Maybe he did. I’m not claiming to know for sure, either way. But they didn’t seem to think so, or else — it seems to me — they could and would have mentioned that. And they can’t be accused of a “Catholic bias” because they are Lutherans.

One can believe in a doctrine, while not thinking a celebration of it is required or pious. And Luther explained in both 1532 and 1544 that what he objected to was the invocation of Mary in the context of the feast. So he wanted to ditch the feast, not the Assumption itself. He says there is nothing in Scripture about it, yet still believes it, so it has to be on the authority of the Church and tradition. In so doing, he makes a temporary exception to sola Scriptura, his rule of faith, which is fascinating, too.

In fact (I must mention, as an apologist), Scripture is not totally silent on the matter. I think a theological/biblical case can be made for it, as a possibility: one that is in harmony with other events in the Bible. But it’s speculative. If indeed Mary was free from sin and immaculately conceived, which can largely be argued from the Bible, then it follows that she would not undergo the decay of death — the penalty for sin (Genesis 3:16-19). Mary would be the exception and the forerunner of the resurrection that all who are saved will experience (1 Corinthians 15:12-23; cf. Matthew 27:52-53).

We have fairly analogous cases of dramatic “going-up-to-heaven” events: Enoch (Hebrews 11:5; cf. Genesis 5:24), Elijah (2 Kings 2:1, 11), and many during the Second Coming (1 Thessalonians 4:15-17), none of whom died. Others went up to heaven after having died: the two witnesses of Revelation (11:7-12) and, of course, our Lord Jesus Himself. Catholics aren’t required to believe that Mary didn’t die.