The leader of this movement was a Syrian, Serene (Serenus) by name, who called himself the Messiah (about 720). He promised the Jews to put them into possession of the Holy Land, having first, of course, expelled the Mahometans. This attempt to regain their long-lost independence was perhaps occasioned by the fanatical Caliph Omar II (717–720). That bigoted prince, who had been raised to the throne by the intrigues of a zealous reader of the Koran, had re-enacted the restrictive laws of his predecessor, Omar I (the covenant of Omar), which had fallen into oblivion under the politic Ommiyyades. After his accession to the throne, he wrote to his governors as follows: "Do not pull down a church or a synagogue, but do not allow new ones to be built within your provinces." Omar devoted himself to making proselytes, holding out attractive promises to the new converts, or unceremoniously compelling both Jews and Christians to embrace Islam. It was probably for this reason that the Jews were disposed to support the false Messiah, and to lend credence to his representations that he would make them free again in the land of their fathers, and exterminate their enemies. Upon his banner Serene inscribed the release from Talmudical ordinances; he abolished the second day's celebration of the festivals, the prescribed forms of prayer, and the laws of the Talmud relating to food: he permitted the use of wine obtained from non-Jews, and sanctioned marriage between persons of nearer relationship than was allowed by the Talmud, as also celebration of marriages without a marriage-contract. It is probable that this hostility towards the Talmud gained him many adherents.
Serene's fame spread as far as Spain, and the Jews of that country resolved to abandon their property and to place themselves under the leadership of the pseudo-Messiah. Hardly ten years after the Jews of Spain had been delivered from the yoke of the Visigoths by the conquests of the Mahometans, they, or at least many of them, were desirous of again abandoning their newly-acquired fatherland. It appears that they were dissatisfied with the rule and administration of the Mahometan governors. As they had rendered signal services to the Arabs in the conquest of the Peninsula, they probably expected particular consideration and distinction, and instead of this they were impoverished equally with the Christians. Serene's fate was miserable, as indeed he deserved. He was captured and brought before the Caliph Yezid, Omar II's successor, who put an end to his Messianic pretensions by propounding insidious questions to him, which he was unable to answer. Serene is said, however, to have denied before the Caliph that he had had any serious designs, but that he only intended to make game of the Jews; whereupon the Caliph handed him over to the Jews for punishment. Many of his adherents, repenting of their easy credulity, desired to rejoin the communities from which they had severed themselves by infringement of the Talmudical ordinances. The Syrian communities were doubtful, however, whether they ought to re-admit their repentant brethren into their midst, or whether they ought not to be treated as proselytes. They referred the matter, therefore, to Natronaï ben Nehemiah, surnamed Mar-Yanka, the principal of the college at Pumbeditha, and successor of Mar-Raba (719–730). Natronaï's decision concerning the reception of Serene's adherents was conceived in a liberal spirit, and ran as follows: According to the laws of the Talmud, there is nothing to prevent them from being re-admitted by the communities and being treated as Jews; but they are to declare openly in the synagogues their sorrow and repentance, and to promise that their future conduct shall be pious and in accordance with the precepts of the Talmud, and in addition they are to suffer the punishment of flogging. At that time there were also other apostates, who went so far as to disregard the Biblical precepts concerning the Sabbath, the ritual for slaughtering cattle, the eating of blood, and the intermarrying of near relations. It is not known, however, in what country these people lived. Without declaring either for Christianity or Islam, they had entirely severed their connection with Judaism. When some of these sought re-admission into the fold of Judaism, Natronaï was again asked for his opinion. He said, "It is better to take them under the wings of God than to cast them out."
At about this time the Jews of the Byzantine empire were subjected to severe persecution, from the effects of which they did not for a long time recover, and this, too, at the hands of a monarch from whom they had least expected hostile treatment. Leo, the Isaurian, the son of rude peasant parents, having had his attention drawn by the Jews and the Arabs to the idolatrous character of the image-worship which obtained in the churches, had undertaken a campaign with the intention of destroying these images. Being denounced, however, before the uncultivated mob as a heretic and a Jew by the image-worshiping clergy, Leo proceeded to vindicate his orthodoxy by persecuting the heretics and the Jews. He issued a decree commanding all the Jews of the Byzantine empire and the remnant of the Montanists in Asia Minor to embrace the Christianity of the Greek Church, under pain of severe punishment (723). Many Jews submitted to this decree, and reluctantly received baptism; they were thus less steadfast than the Montanists, who, in order to remain faithful to their convictions, assembled in their house of prayer, set fire to it, and perished in the flames. Such of the Jews as had allowed themselves to be baptized were of the opinion that the storm would soon blow over, and that they would be permitted to return to Judaism. It was, therefore, only outwardly that they embraced Christianity; for they observed the Jewish rites in secret, thereby subjecting themselves to fresh persecutions. Thus the Jews of the Byzantine empire pined away under unceasing petty persecution, and for a time they are hidden from the view of history.
Many Jews of the Byzantine empire, however, escaped compulsory baptism by emigration. They quitted a country in which their forefathers had settled long before the rise of that Church which had so persistently persecuted them. The Jews of Asia Minor chose as their home the neighboring Cimmerian or Tauric peninsula (the Crimea), whose uncivilized inhabitants, of Scythian, Finnish and Sclavonian origin, practised idolatry. These Alani, Bulgarians and Chazars were, however, not jealous of men of other race and of a different belief who settled in their vicinity. Thus, side by side with the Jewish communities which had existed from early times, there arose new communities on the shores of the Black Sea and the Straits of Theodosia (Kaffa), and in the interior, in Sulchat (Solgat, now Eski-Crimea), in Phanagoria (now Taman), and on the Bosporus (Kertch), which lies opposite. From the Crimea the Greek Jews spread towards the Caucasus, and the hospitable countries of the Chazars on the west coast of the Caspian Sea and at the mouth of the Volga (Atel). Jewish communities settled in Berdaa (Derbend), at the Albanian Gates, in Semender (Tarki), and finally in Balanyiar, the capital of the land of the Chazars. By their energy, ability and intelligence, the Greek-Jewish emigrants speedily acquired power in the midst of these barbarian nations, and prepared the way for an important historical event.
Hardly thirty years after the fall of the false Messiah, Serene, an anti-Talmudical movement, coupled with Messianic enthusiasm, was again set on foot, but this time on a different scene. The prime mover was a fantastic and warlike inhabitant of the Persian town of Ispahan, one Obaiah Abu-Isa ben Ishak. He was not an ignorant man; he understood the Bible and the Talmud, and was capable of expressing his thoughts in writing. It is said that he was made aware of his call to an exalted vocation by a sudden cure from leprosy. Abu-Isa did not proclaim himself to be the Messiah, but asserted that he was the forerunner and awakener (Dâï) who was to prepare for the coming of the Messiah. His views concerning the office of precursor of the Messiah were, indeed, altogether peculiar. He taught that five forerunners would precede the Messiah, and that each one would be more perfect than his predecessor. He considered himself the last and most perfect of the five, and of equal merit with the Messiah. He assumed his vocation in good earnest, and announced that God had called him to free the Jewish race from the yoke of the nations and of unjust rulers.
The Messianic precursor of Ispahan found many partisans, 10,000 Jews, it is said, gathering around him for the purpose of aiding him in his work of deliverance. To them Abu-Isa expounded a form of Judaism differing in some respects from that accepted at the time; the points of difference,