"The veneration of Mary is inscribed in the very depths of the human
heart." -Martin Luther (Sermon, September 8, 1522).
"[She is the] highest woman and the noblest gem in Christianity after
Christ. ..She is nobility, wisdom, and holiness personified. We can
never honor her enough. Still honor and praise must be given to her in
such a way as to injure neither Christ nor the Scriptures." -Martin
Luther (Sermon, Christmas, 1531).
"No woman is like you. You are more than Eve or Sarah, blessed above
all nobility, wisdom, and sanctity." -Martin Luther (Sermon, Feast of
the Visitation. 1537).
"One should honor Mary as she herself wished and as she expressed it in
the Magnificat. She praised God for his deeds. How then can we praise
her? The true honor of Mary is the honor of God, the praise of God's
grace.. .Mary is nothing for the sake of herself, but for the sake of
Christ...Mary does not wish that we come to her, but through her to
God." -Martin Luther (Explanation of the Magnificat, 1521)
Luther speaks of the Blessed Virgin Mary as also the "Spiritual
Mother" for all Christians, the first of the Christians who consented
to the Angel's Word, pondered all these things in her heart, and whose
own soul was pierced as Simeon prophesied:
"It is the consolation and the superabundant goodness of God, that man
is able to exult in such a treasure. Mary is his true Mother, Christ is
his brother. God is his father." -Martin Luther (Sermon. Christmas,
1522)
"Mary is the Mother of Jesus and the Mother of all of us even though it
was Christ alone who reposed on her knees...If he is ours, we ought to
be in his situation; there where he is, we ought also to be and all that
he has ought to be ours, and his mother is also our mother." - Martin
Luther (Sermon, Christmas, 1529).
Fr. Peters: To the nervous Lutherans reading this let me say. Of course, and let me say it again, of course none of these affirmations not explicitly stated in Scripture (immaculate conception, perpetual virginity, or the assumption) could ever be required belief or be set as doctrine along side, for example, the creed. No Lutheran and not even Luther was saying this. But that did not and does not preclude one from believing such. Where Lutherans differ from Protestants is that we allow these traditions to be held as private opinion which, while not found in Scripture, do not contradict it. Roman Catholics, on the other hand, do not affirm Scripture as both source and norm of all doctrine and therefore regard tradition to be an equal source of doctrine (tradition which does not conflict with Scripture). For Lutherans it is a matter of private faith but for Roman Catholics it is a matter of public doctrine. (http://pastoralmeanderings.blogspot.com/2014/03/luther-on-annunciation.html)