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 of Lugdunum in the 2nd century and later by Bishop Eusebius of Caesarea. In the third century, Bishop Cyprian of Carthage demanded Jews to be expelled from his diocese at the point of the sword, and Bishop Hosius of Corduba with other clergymen restricted relations with Jews at the Council of Elvira in the early fourth century. Bishop Ambrose of Milan, Bishop Gregory of Nyssa, and John Chrysostom also blamed Jews for the death of Christ in the late fourth century.

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 defended the bishop responsible for the destruction of Callinicum's synagogue and Emperor Theodosius I did not punish him.

Cyril, Bishop of Alexandria, expelled Jews from Alexandria in 415. He described Jews as “the most deranged of all men”, “senseless”, “blind”, “uncomprehending”, “demented”, “foolish God haters”, “killers of the Lord”, “unbelievers”, and “irreligious.” In 418, Bishop Severus of Menorca forcefully converted Jews, which he claimed he converted hundreds of, to Christianity and destroyed their synagogue.

During his years as the Pope from 590 to 604, Gregory I complained of Jews being stubborn and described them as “preachers of Antichrist”. He considered Judaism as Jewish superstition, depravity, and faithlessness and was disgusted with converts that “return to their vomit.” Gregory also opposed Jews having ownership of Christian slaves. In 598, Bishop Victor of Palermo confiscated synagogues and converted them to churches.

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]. ...”

Roman emperors
Under the rule of Constantine I, the first Christian Roman emperor, Jews were persecuted. Jewish people were forbidden to own Christian slaves and to circumcise slaves. He ordered that the property of Christians that embraced Judaism to be confiscated and he issued a law that forbade marriages between Jews and Christians which was punishable to Jewish people with the death penalty. Constantine also prohibited Jews from visiting and settling in Jerusalem and from proselytizing. All Roman emperors after Constantine, except Julian, were Christian.

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.

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.

Emperor of the western part of the Roman Empire, Honorius, issued decrees in the late fourth century that attempted to restrict the self-administration of Jewish communities and in 408 restricted Jews from disrespecting Christianity during Purim. In 409, he issued a law condemning Christian conversion to Judaism stating “... it is graver than death and crueler than massacre when someone abjures the Christian faith and becomes polluted with the Jewish incredulity. ...” and called Judaism “the Jewish perversity”. He later prohibited the construction of new synagogues and prohibited Jews from the purchase of Christian slaves. Honorius, Emperor Theodosius II, and the latter emperors, Valentinian III, Justin, and Justinian restricted Jews from employment in the bureaucracy and the army.

In the 5th century, Theodosius II, emperor of the eastern part of the Roman Empire, restricted Jews from holding any advantageous office of honor, forbade the building of new synagogues, and in the late 430s decreed that any Jew that converted a Christian to Judaism would be punished with their property being confiscated and the death penalty. The Theodosian Code prohibited Jews from the purchase of Christian slaves.

Emperor Justinian I, in the 6th century, prohibited Jews from bearing witness against orthodox Christians in court. Under the Code of Justinian, converting to Judaism was punishable by death and confiscation of the offender's goods, and he prohibited Jews from holding administrative and honorary offices, and from municipal dignities and legal practice. He also prohibited the construction of new synagogues, ordered the conversion of synagogues in Africa into churches, compelled Jews to keep Passover on the same day as the Christians observed Easter, forbade Jews from reading the Mishna, and prohibited Jewish ownership of Christian slaves.

Multiple emperors wanted the forced conversion of Jews to Christianity including Phocas and Heraclius in the seventh century, Leo III in the eighth century, Basil I in the ninth century, Romanos I Lekapenos in the tenth century, and John III Ducas Vatatzes in the 13th century. Heraclius also had Jews expelled from Jerusalem, and, in the 11th century, Emperor Constantine X Doukas banished Jews from Constantinople.