Perhaps the Jews will declare that the Ishmaelites and Edomites, etc., do not observe the rite of circumcision as strictly as they do. In addition to cutting off the foreskin of a male child, the Jews force the skin back on the little penis and tear it open with sharp fingernails, as one reads in their books. Thus they cause extraordinary pain to the child, without and against the command of God, so that the father, who should really be happy over the circumcision, stands there and weeps as his child’s cries pierce his heart. We answer roundly that such an addendum is their own invention, yes, it was inspired by the accursed devil, and is in contradiction to God’s command, since Moses says in Deuteronomy 4 [:2] and 12 [:32]: “You shall not add to the word which I command you, nor take from it.” With such a devilish supplement they ruin their circumcision, so that in the sight of God no other nation practices circumcision less than they, since with such wanton disobedience they append and practice this damnable supplement.
Martin Luther, Luther’s Works, Vol. 47: The Christian in Society IV, ed. Jaroslav Jan Pelikan, Hilton C. Oswald, and Helmut T. Lehmann, vol. 47 (Philadelphia: Fortress Press, 1999), 152–153.