Persecution of Jews in the Roman and Byzantine Empires

Church Fathers and Christian clergy
The blame on Jews as a people holding the responsibility for killing Jesus Christ or Jewish deicide was expressed by Justin Martyr, Bishop Melito of Sardis, and Bishop Irenaeus in the 2nd century and later by Bishop Eusebius of Caesarea. In the late 4th century, Bishop Ambrose of Milan, Bishop Gregory of Nyssa, and John Chrysostom also blamed Jews for the death of Christ.

A Christian mob led by a bishop looted and burned down a synagogue in Callinicum in 388. In the same year, another bishop, Philaster of Brescia encouraged the populace of Rome to set fire to a synagogue. Ambrose of Milan defended the bishop responsible for the destruction of Callinicum's synagogue and Emperor Theodosius I did not punish him.

Christian church councils
The ecclesiastical Council of Elvira, during the early fourth century, prohibited eating with Jews (Canon 50), prohibited marriage between Jewish males with Christian females (Canon 16), and prohibited fields from being blessed by Jews (Canon 49).

The Council of Nicaea was convened by Constantine in 325 and mandated the separation of the celebration of Easter from the Jewish calendar. Constantine on the results of the Council of Nicaea: “... It was declared to be particularly unworthy for this, the holiest of all festivals, to follow the custom of the Jews, who had soiled their hands with the most fearful of crimes, and whose minds were blinded. ... We ought not ... to have anything in common with the Jews, for the Savior has shown us another way; our worship follows a more legitimate and more convenient course; and consequently, in unanimously adopting this mode, we desire, dearest brethren, to separate ourselves from the detestable company of the Jews, for it is truly shameful for us to hear them boast that without their direction we could not keep this feast. How can they be in the right, they who, after the death of the Savior, have no longer been led by reason but by wild violence, as their delusion may urge them? They do not possess the truth in this Easter question; for, in their blindness and repugnance to all improvements, they frequently celebrate two passovers in the same year. We could not imitate those who are openly in error. How, then, could we follow these Jews, who are most certainly blinded by error? for to celebrate the passover twice in one year is totally inadmissible. But even if this were not so, it would still be your duty not to tarnish your soul by communications with such wicked people [the Jews]. ...”

Constantine I
Under the rule of Constantine I, the first Christian Roman emperor, Jews were persecuted. Jewish people were forbidden to perform the rite of circumcision on slaves or to own Christian slaves, and the death penalty was imposed on those that embraced Judaism and Jews versed in the Law who aided them. He issued a law that forbade marriages between Jews and Christians and imposed the death penalty on Jewish people who should break this law. Constantine's Edict of Milan in the 4th century caused Jews to lose many rights and they were no longer permitted to live in Jerusalem or to proselytize. All Roman emperors after Constantine, except Julian, were Christian.

Constantius II
Constantius II was a Christian Roman emperor during the 4th century and was the son of Constantine. He created laws that were beneficial to the Christian clergy and limited the rights of the Jews. He forbade intermarriage between Jewish males and Christian females under penalty of death, forbade Jews from owning slaves, and punished those that converted from Christianity to Judaism with their property being confiscated.

Theodosius I
Emperor Theodosius I in 384 prohibited the purchase of Christian slaves by Jews and prohibited intermarriage between Jews and Christians. The bishop responsible for burning down a synagogue in Callinicum in 388 was not punished by the emperor.