The issue of Luther’s (early) attitudes to Jews is often raised, with a
question as to source/s. Here’s one:

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, Volume 47: The Christian in Society IV,
(Philadelphia: Fortress Press, 1971). “The Jews and their Lies” pp 268
ff

If you are interested in more information, see
http://www.us-israel.org/jsource/anti-semitism/Luther_on_Jews.html
from which the above quotation was taken, and
http://www.luther.de/e/juden.html
which is a Lutheran site with links to similar material.