“To judaize, namely to observe Saturday, or other Jewish ceremonies, is mortal [sin]: because that pertains to the superstition of a false divine cult, according to Cajetan, in his summa. If however one observes Saturday, not for the purposes of a Jewish rite, but for some other pious reason, such as to venerate the Blessed Virgin Mary, he would not sin mortally. To converse with Jews is forbidden at Canon Law, in many places in the capitular De Judaeis etc. 28 q. 1 Capitular Nullus, etc and all of them regarding assiduous, and familiar conversation, due to the danger of subversion, and especially in ten cases is it forbidden: First, to live with them; Second, to eat with them; Third, to bathe with them; Fourth, to call upon them for medical care; Fifth, to accept their medicine; Sixth, to feed their children in their houses; Seven, to serve them, as employees; Eight, to be their slaves; Nine, for them to hold public office amongst Christians; Ten, to eat their azyme [matzo]. To tolerate them in public office is mortal, because this disparages the dignity of the Christian Faith, and for that reason is it forbidden. The same, because this would cause too great a familiarity, and consequently a danger of subversion, as supra. I say the same for the consumption of their azyme. To do all of that is mortal. To eat food with them when one has a choice is never permitted, apart from extreme necessity.” ~ Fra Bartolomeo Fumo, O.P., Inquisitor General for the Duchies of Parma and Piacenza, +1542 A.D. (Citation from the medieval Inquistor’s manual explaining what can and cannot be done vis-à-vis Jews, based on the canonical legislation promulgated by Pope Gregory IX in A.D. 1234, in the capitular “De Judaeis” [Of the Jews].)