At the beginning of his career, Luther was apparently sympathetic to Jewish resistance to the Catholic Church. He wrote, early in his career
The Jews are blood-relations of our Lord; if it were proper to boast of flesh and blood, the Jews belong more to Christ than we. I beg, therefore, my dear Papist, if you become tired of abusing me as a heretic, that you begin to revile me as a Jew.
But Luther expected them to convert to his purified Christianity. When they did not, he turned violently against Jews.
A number of points must, however, be made. The most important concerns the language used. Luther used violent and vulgar language throughout his career: he was not a man to say "manure" when he meant "shit". We do not expect religious figures to use this sort of language in the modern world, but it was not uncommon in the early 16th century. While there is little doubt that Christian anti-Semitism laid the social and cultural basis for modern anti-Semitism, modern anti-Semitism does differ in being based on pseudo-scientific notions of race. The Nazis imprisoned and killed Jews who had converted to Christianity: Luther would have welcomed them. None of this justifies what follows, but it may help to comprehend what is happening.
I had made up my mind to write no more either about the Jews or against them. But since I learned that these miserable and accursed people do not cease to lure to themselves even us, that is, the Christians, I have published this little book, so that I might be found among those who opposed such poisonous activities of the Jews who warned the Christians to be on their guard against them….
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Learn from this, dear Christian, what you are doing if you permit the blind Jews to mislead you. Then the saying will truly apply, "When a blind man leads a blind man, both will fall into the pit" [cf. Luke 6:39]. You cannot learn anything from them except how to misunderstand the divine commandments...
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Therefore be on your guard against the Jews, knowing that wherever they have their synagogues, nothing is found but a den of devils in which sheer self-glory, conceit, lies, blasphemy, and defaming of God and men are practiced most maliciously and veheming his eyes on them.
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Moreover, they are nothing but thieves and robbers who daily eat no morsel and wear no thread of clothing which they have not stolen and pilfered from us by means of their accursed usury. Thus they live from day to day, together with wife and child, by theft and robbery, as arch-thieves and robbers, in the most impenitent security.
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Did I not tell you earlier that a Jew is such a noble, precious jewel that God and all the angels dance when he farts?
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What shall we Christians do with this rejected and condemned people, the Jews? Since they live among us, we dare not tolerate their conduct, now that we are aware of their lying and reviling and blaspheming. If we do, we become sharers in their lies, cursing and blaspemy. Thus we cannot extinguish the unquenchable fire of divine wrath, of which the prophets speak, nor can we convert the Jews. With prayer and the fear of God we must pratice a sharp mercy to see whether we might save at least a few from the glowing flames. We dare not avenge ourselves. Vengenance a thousand times worse than we could wish them already has them by the throat. I shall give you my sincere advice:
First to set fire to their synagogues or schools and to bury and cover with dirt whatever will not burn, so that no man will ever again see a stone or cinder of them. This is to be done in honor of our Lord and of Christendom, so that God might see that we are Christians, and do not condone or knowingly tolerate such public lying, cursing, and blaspheming of his Son and of his Christians. For whatever we tolerated in the past unknowingly - and I myself was unaware of it - will be pardoned by God….
Second, I advise that their houses also be razed and destroyed. For they pursue in them the same aims as in their synagogues. Instead they might be lodged under a roof or in a barn, like the gypsies. This will bring home to them that they are not masters in our country, as they boast, but that they are living in exile and in captivity, as they incessantly wail and lament about us before God.
Third, I advise that all their prayer books and Talmudic writings, in which such idolatry, lies, cursing and blasphemy are taught, be taken from them.
Fourth, I advise that their rabbis be forbidden to teach henceforth on pain of loss of life and limb. For they have justly forfeited the right to such an office by holding the poor Jews captive with the saying of Moses (Deuternomy 17 [:10 ff.]) in which he commands them to obey their teachers on penalty of death, although Moses clearly adds: "what they teach you in accord with the law of the Lord." Those villains ignore that. They wantonly employ the poor people's obedience contrary to the law of the Lord and infuse them with this poison, cursing, and blasphemy….
Fifth, I advise that safe-conduct on the highways be abolished completely for the Jews. For they have no business in the countryside, since they are not lords, officials, tradesmen, or the like. Let they stay at home.
Sixth, I advise that usury be prohibited to them, and that all cash and treasure of silver and gold be taken from them and put aside for safekeeping. The reason for such a measure is that, as said above, they have no other means of earning a livelihood than usury, and by it they have stolen and robbed from us all they possess.
Seventh, I commend putting a flail, an ax, a hoe, a spade, a distaff, or a spindle into the hands of young, strong Jews and Jewesses and letting them earn their bread in the sweat of their brow, as was imposed on the children of Adam (Gen 3[:19]}. For it is not fitting that they should let us accursed Goyim toil in the sweat of our faces while they, the holy people, idle away their time behind the stove, feasting and farting, and on top of all, boasting blasphemously of their lordship over the Christians by means of our sweat. No, one should toss out these lazy rogues by the seat of their pants.
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But what will happen even if we do burn down the Jews' synagogues and forbid them publicly to praise God, to pray, to teach, to utter God's name? They will still keep doing it in secret. If we know that they are doing this in secret, it is the same as if they were doing it publicly. for our knowledge of their secret doings and our toleration of them implies that they are not secret after all and thus our conscience is encumbered with it before God.
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Accordingly, it must and dare not be considered a trifling matter but a most serious one to seek counsel against this and to save our souls from the Jews, that is, from the devil and from eternal death. My advice, as I said earlier, is:
First, that their synagogues be burned down, and that all who are able toss in sulphur and pitch; it would be good if someone could also throw in some hellfire. That would demonstrate to God our serious resolve and be evidence to all the world that it was in ignorance that we tolerated such houses, in which the Jews have reviled God, our dear Creator and Father, and his Son most shamefully up till now but that we have now given them their due reward.
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I wish and I ask that our rulers who have Jewish subjects exercise a sharp mercy toward these wretched people, as suggested above, to see whether this might not help (though it is doubtful). They must act like a good physician who, when gangrene has set in, proceeds without mercy to cut, saw, and burn flesh, veins, bone, and marrow. Such a procedure must also be followed in this instance.
Burn down their synagogues, forbid all that I enumerated earlier, force them to work, and deal harshly with them, as Moses did in the wilderness, slaying three thousand lest the whole people perish. They surely do not know what they are doing; moreover, as people possessed, they do not wish to know it, hear it, or learn it. There it would be wrong to be merciful and confirm them in their conduct. If this does not help we must drive them out like mad dogs, so that we do not become partakers of their abominable blasphemy and all their other vices and thus merit God's wrath and be damned with them. I have done my duty. Now let everyone see to his. I am exonerated."
From Luther's Works, Republished in volume 47: The Christian in Society IV, (Philadelphia: Fortress Press, 1971). pp 268-293