Luther wrote to the Archbishop protesting the sale of indulgences to finance the building of a new cathedral. The Archbishop, of course, was one of the people who had authorized the sale of indulgences for that purpose. The date and function of the letter are as important as its contents: note the date and the reference to attached Disputations.

To the Most Reverend Father in Christ and Most Illustrious Lord, Albrecht of Magdeburg and Mainz, Archbishop and Primate of the Church, Margrave of Brandenburg, etc., his own lord and pastor in Christ, worthy of reverence and fear, and most gracious.

[...] Works of piety and love are infinitely better than indulgences, and yet these are not preached with such ceremony or such zeal; nay, for the sake of preaching the indulgences they are kept quiet, though it is the first and the sole duty of all bishops that the people should learn the Gospel and the love of Christ, for Christ never taught that indulgences should be preached. How great then is the horror, how great the peril of a bishop, if he permits the Gospel to be kept quiet, and nothing but the noise of indulgences to be spread among his people! Will not Christ say to them, “straining at a gnat and swallowing a camel”? In addition to this, Most Reverend Father in the Lord, it is said in the Instruction to the Commissaries which is issued under your name, Most Reverend Father (doubtless without your knowledge and consent), that one of the chief graces of indulgence is that inestimable gift of God by which man is reconciled to God, and all the penalties of purgatory are destroyed. Again, it is said that contrition is not necessary in those who purchase souls [out of purgatory] or buy confessionalia.

But what can I do, good Primate and Most Illustrious Prince, except pray your Most Reverend Fatherhood by the Lord Jesus Christ that you would deign to look [on this matter] with the eye of fatherly care, and do away entirely with that treatise and impose upon the preachers of pardons another form of preaching; lest, perchance, one may some time arise, who will publish writings in which he will confute both them and that treatise, to the shame of your Most Illustrious Sublimity. I shrink very much from thinking that this will be done, and yet I fear that it will come to pass, unless there is some speedy remedy.

These faithful offices of my insignificance I beg that your Most Illustrious Grace may deign to accept in the spirit of a Prince and a Bishop, i.e., with the greatest clemency, as I offer them out of a faithful heart, altogether devoted to you, Most Reverend Father, since I too am a part of your flock. May the Lord Jesus have your Most Reverend Fatherhood eternally in His keeping. Amen.

From Wittenberg on the Vigil of All Saints, MDXVII.

If it please the Most Reverend Father he may see these my Disputations, and learn how doubtful a thing is the opinion of indulgences which those men spread as though it were most certain.

To the Most Reverend Father, Brother Martin Luther

On February 2, 1538, Luther related the following story at table:

God has led us along in a wonderful way and has guided me, even without my knowing it, for more than twenty years. How troublesome it was in the beginning, as we went out to Kemberg, after All Saints' in 1517. It was then that I undertook to write against the blatant errors on indulgences. But Dr. Hieronymous Schurff tried to stop me. “What! You want to attack the pope? That they will not allow!” But I said, “And if they must allow it?”

In the 1540s, Johannes Sleidan (1506-1556) emerged as the first true historian of the Reformation. An obsessive collector of documents, Sleidan was engaged by Prince Philip of Hesse to write a history of the evangelical reform movement, then not yet thirty years old. The first volume appeared in 1545. After many delays, including a stint at the Council of Trent, which he attended as a representative of the city of Strassbourg, Sleidan finally finished his account in 1554. Here is Sleidan's description of the events surrounding the publication of the Ninety-Five Theses, from Edmund Bohun's translation of 1689:

That he might, therefore, proceed in his Design with better Success, on the last of October, he wrote to Albert of Brandenburg, Archbishop of Mentz, accquainting him with what they [i.e., the reformers] Taught; and Complaining that the People were so persuaded, as that having purchased these Indulgences by Money, they needed no more doubt of Salvation, as if no Crime could be committed which was not by that means Pardoned; and as if the Souls which were Tormented in the Fire of Purgatory, so soon as the Money was cast into the Box, were presently discharged of their Pains, and took their Fleight streight up to Heaven. He tells him, That Christ commanded the Gospel to be Preached; and that it was the proper Office of Bishops, to instruct the People in the Right Way: Wherefore he puts him in Mind of his Duty, and prays him taht he would use his Authority in suppressing those Books, and enjoyning the Preachers to teach better Doctrin, lest it might give Occasion to some more grievous Dissension, which would undoubtedly happen, if they were not restrained. The Reason why he wrote to him, was, Because he being also Bishop of Magdeburg, it belonged to him to take care of these things. With this Letter, he also sent the Theses, which for Disputation sake, he had lately published in Wittenberg, to the number of ninety five, wherein he fully handled the Doctrin of Purgatory, true Penance, and the Office of Charity, and censured the extravagant Preaching of the Collectors; but only for discovering the Truth, as has been said [...]. The Archbishop of Mentz made no answer to these things [...].

But when no Man of the contrary Part came to the Disputation proposed at Wittemberg, and that the Theses we mentioned, were read by many with great Applause, Luther wrote a very large Explication of them, and sent it, first to Jerome Bishop of Brandenburg, to whose Jurisdiction he belonged, and, then to John Stupitz Provincial of the Augustine Friers, praying him to have it transmitted to the Pope: Nay, in the Month of June [1518], he wrote to Pope Leo himslef, informing him, That these Collectors, relying upon, or abusing his Authority, taught very rashly, and behaved themselves covetously [...].