[De communione et conversatione Iudaeorum et Christianorum]

"To give your daughter," etc. Here the text says that if anyone is joined to Jewish depravity in conjugal society, whether a Christian man to a Jewess, or a Jewish woman to a Christian man, and they are mixed in carnal consort, whoever of them has committed such a sin is known to be separated from the Christian community and from the communion of the church. And to avoid that sin, the Church declares in a general council, as found in the chapter "In nonnullis provinciis," that all Jews of either sex in all provinces of the Christians must be distinguished at all times from the persons of the faithful by the quality of their attire. It is good that they wear such signs by which they are notoriously known by the faithful. The text says that since that difference is not in their attire, it happens sometimes that through error Christians are mixed with the women of Jews or Saracens, and Jews or Saracens with the women of Christians. Therefore, so that such damned excesses of mixture cannot have a refuge of excuse through the veil of error, it is decreed that such things must be observed. And that statute was renewed in the last provincial synod of Mainz, presided over by the Cardinal of Saint Peter in Chains, Lord Nicholas of Cusa, and fortified with heavy penalties, and it is practiced in many places because the sin of the flesh between Jews and Christians has flourished too much. Therefore, as is known from the profession, harlot and matron, male and female are distinguished by clothes and hair, and free men from servants by a cap, the gloss says; so too, Jews and Christians will have a patent distinction in their attire, just as the law ordained regarding the fringes and corners of cloaks through Moses (Numbers 15). Whence also the Samaritan woman knew the Lord (John 4) by speech and clothing, and by the sect and race of the Jews.

The fourth admonition: That Jews are not permitted to erect new synagogues. So writes Gregory to the Bishop of Januensis, as the chapter "Iudaei" and "Civitate" (de Iudaeis) says: just as legal definition does not suffer the Jews to erect new synagogues, so it permits them to have the old ones without disturbance. So, it is said in the same place (law 3, c. "Consuluit"): "You ought not to suffer Jews to construct new synagogues where they have not had them; however, if the old ones have rotted or threaten ruin, it can be equanimously tolerated that they rebuild them."