“I am frightened now, seeing that certain of you have desired to change the condition of important matters, introducing a new festival unknown to the Church, unapproved by reason, unjustified by ancient tradition. Are we really more learned and more pious than our fathers? You will say, ‘One must glorify the Mother of God as much as Possible.’ This is true; but the glorification given to the Queen of Heaven demands discernment. This Royal Virgin does not have need of false glorifications, possessing as She does true crowns of glory and signs of dignity. Glorify the purity of Her flesh and the sanctity of Her life. Marvel at the abundance of the gifts of this Virgin; venerate Her Divine Son; exalt Her Who conceived without knowing concupiscence and gave birth without knowing pain. But what does one yet need to add to these dignities? People say that one must revere the conception which preceded the glorious birth-giving; for if the conception had not preceded, the birth-giving also would not have been glorious. But what would one say if anyone for the same reason should demand the same kind of veneration of the father and mother of Holy Mary? One might equally demand the same for Her grandparents and great-grandparents, to infinity. Moreover, how can there not be sin in the place where there was concupiscence? All the more, let one not say that the Holy Virgin was conceived of the Holy Spirit and not of man. I say decisively that the Holy Spirit descended upon Her, but not that He came with Her…I say that the Virgin Mary could not be sanctified before Her conception, inasmuch as She did not exist. If, all the more, She could not be sanctified in the moment of Her conception by reason of the sin which is inseparable from conception, then it remains to believe that She was sanctified after She was conceived in the womb of Her mother. This sanctification, if it annihilates sin, makes holy Her birth, but not Her conception. No one is given the right to be conceived in sanctity; only the Lord Christ was conceived of the Holy Spirit, and He alone is holy from His very conception. Excluding Him, it is to all the descendants of Adam that must be referred that which one of them says of himself, both out of a feeling of humility and in acknowledgement of the truth: Behold I was conceived in iniquities (Ps. 50:7). How can one demand that this conception be holy, when it was not the work of the Holy Spirit, not to mention that it came from concupiscence? The Holy Virgin, of course, rejects that glory which, evidently, glorifies sin. She cannot in any way justify a novelty invented in spite of the teaching of the Church, a novelty which is the mother of imprudence, the sister of unbelief, and the daughter of lightmindedness”
Bernard of Clairvaux, Epistle 174, in The Letters of St Bernard of Clairvaux (Sutton, 1998)[click on post title to view].
"Bernard of Clairvaux, (1090 – August 20, 1153) was a French abbot and the primary builder of the reforming Cistercian order...At the 800th anniversary of his death, Pope Pius XII issued an encyclical on Bernard, Doctor Mellifluus in which he labeled him 'The Last of the Fathers'....Bernard also held some doctrines which the Reformers would later rekindle at the beginnings of the Protestant movement. Some people have therefore equated him with a Protestant before there were Protestants. In truth he held to a mix of the Reformers' doctrines and the doctrines of the Roman Catholic Church of his day.Bernard fought against the doctrine of the Immaculate Conception of Mary.Also of great importance to the Reformers would be Bernard's conception of justification. Calvin quotes Bernard several times to show the historical valididy of Sola Fide, which Luther described as 'the article upon which the church stands or falls'. Calvin also quotes him extensively in setting forth his doctrine of a forensic alien righteousness,or as it is commonly called imputed righteousness" [http://en.wikipedia.org/wiki/Bernard_of_Clairvaux].
Note - The Immaculate Conception of Mary is the Roman Catholic dogma that the the Virgin Mary was conceived without any stain ("macula" in Latin) of original sin. The Catholic Encyclopedia of 1907 frankly admitted that "[n]o direct or categorical and stringent proof of the dogma can be brought forward from Scripture" (http://oce.catholic.com/index.php?title=Immaculate_Conception#II._THE_HOLY_SCRIPTURE), and denied that the allegorical interpretation of passages such as Genesis 3:15 are an adequate scriptural foundation for the dogma. At best, it says, such passages serve as corroborative evidence. The witness of tradition is ambiguous, with many Fathers either ignorant of the belief or flatly denying it, including such prominent medieval theologians as Bernard, Bonaventure and Aquinas. The belief seems to have been purely an outgrowth of popular piety down through the centuries (even a young Luther was attached to it), and the dogma finally rests on the 'ecclesiastical positivism' of the 1854 papal ex cathedra definition. Indeed, Aquinas had stated that he could only believe the dogma on the basis of the church's authority, which points us to the significance of this dogma as a 'watershed' issue between those who adhere to sola scriptura and those who ascribe to either tradition or the church an authority equal to or above scripture.
Curiously, the belief in Mary's immaculate conception can be found in the Koran (3rd chapter), which fact likely points us to the origins of this dogma in the Marian piety of the Syrian Christians with whom Muhammed interacted as a trader - MH.
I have added new links to essays on Luther and Bernard by Posset, Pedersen and Bell; check the essays column to the right.