The zeal with which the Karaites sought to exalt their creed over Rabbanism had the desired effect of spreading it widely about the middle of the tenth century. They penetrated to Spain, and attained influence in Africa and Asia. We know that the Egyptian Rabbanites accepted much from the Karaites. Moses and Aaron ben Asher, a father and son of Tiberias, exercised a powerful influence at this period (890–950). They were grammarians and Massorets. They wrote on the Hebrew accents and Biblical orthography, but in so clumsy a style and such miserable verse, that their observations are for the most part incomprehensible. But these insignificant works were of no importance, while considerable value attached to the copies of the Bible, which were corrected by them with the greatest care and exactness according to the Massoretic rules, which they had mastered completely. The Ben-Asher copies of the Bible were looked upon as models both by the Karaites and the Rabbanites, and treated as sacred. New copies were afterwards made from these in Jerusalem and Egypt. The Massoretic texts of the Bible now in use are largely derived from Ben-Asher's original copies, because the Rabbanites afterwards overlooked the fact that the scribe was a Karaite.

Saadiah, on the contrary, who had known Ben-Asher, the son, was dissatisfied with these Massoretic works, and wrote a very keen polemic against him. In addition to Saadiah, Ben-Naphtali raised objections against the results of Ben-Asher's Massoretic investigations, though mostly on insignificant points. Nevertheless, the text of the Bible according to the Massorets of Tiberias maintained its superiority. The old Eastern signs for vowels and accents to the Bible text were changed, extended and improved, by the Massoretic school of Ben-Asher.

With the decay of the Exilarchate and of the school of Sora, Asia lost the leadership of Judaism. If Pumbeditha, under Aaron Ibn-Sarjadu, flattered itself that it possessed the supremacy, it was deceived. After Ibn-Sarjadu's death, internal quarrels prepared for its destruction. Nehemiah, the son of Kohen-Zedek, who had been the rival of Ibn-Sarjadu, but had not met with success, obtained the post of head of the school through cunning (960). The college, however, led by the chief Judge Sherira ben Chananya, opposed him. There were a few members and rich laymen who supported Nehemiah, but his opponents refused to recognize him during the whole period of his office (960–968). During the time that the two parties were contending for the Gaonate of Pumbeditha, and with it for the religious authority over the Jews, the four men who had been sent from Sora to collect contributions from the various communities, and who had been taken captive, had founded new schools in Egypt, Africa (Kairuan), Spain and France, and thereby separated these communities from the Gaonate. These four men who caused the seeds of the Talmudic spirit to blossom in various places were: Shemaria ben Elchanan, who was sold by the admiral Ibn-Rumahis in Alexandria, and then being ransomed by the Jewish community, finally reached Misr (Cairo). The second was Chushiel, who was sold on the coast of Africa, and came to Kairuan. The third was probably Nathan ben Isaac Kohen, the Babylonian, who perhaps reached Narbonne. The fourth was Moses ben Chanoch, who underwent more dangers than the other three. He was the only one of the four who was married. His beautiful and pious wife and his young son had accompanied him on his journey, and were taken prisoners together with him. Ibn-Rumahis had set eyes upon the beautiful woman, and designed to violate her. The wife, however, asked her husband in Hebrew whether those that were drowned could hope for resurrection, and when he answered in the affirmative, and confirmed his answer by a verse from the Bible, she threw herself into the sea and was drowned. In deep sorrow and in the garb of the slave, Moses ben Chanoch with his little son was carried to Cordova, where he was ransomed by the Jewish community. They did not imagine that with him Spain obtained the supremacy over the Jews of all other countries. Moses did not betray his deep knowledge of the Talmud to the community into whose midst he had been cast, so that he might not derive any advantage from his knowledge of the Law. He, therefore, at first behaved like any ordinary captive. Moses soon made his way to the school of Cordova, the president of which was Nathan. He was a rabbi and also judge, and possessed but slight Talmudical knowledge, but was regarded as a shining light in Spain. Moses sat near the door in the corner like an ignorant listener. But when he perceived that Nathan, in expounding a passage in the Talmud, made a childish mistake, he modestly ventured to make some objections, in which he betrayed his scholarship. The audience in the school was astounded to find so thorough a Talmudist in the ill-clad captive who had just recovered his freedom.

Moses was called upon to explain the passage in question, and also to solve other difficulties. He did this in a thorough manner, to the intense delight of all present. On that very day Nathan declared before those who were under his jurisdiction, "I can no longer be your judge and rabbi. That stranger, who is now so miserably clothed, must henceforth take my place." The rich community of Cordova immediately chose Moses for their rabbinical chief, gave him rich presents and a salary, and placed a carriage at his disposal. When the admiral Ibn-Rumahis heard that his prisoner was so precious to the community of Cordova, he wished to retract the sale in order to get a higher ransom. The Jews appealed to the just Caliph, Abdul-Rahman III, through the Jewish statesman Chasdaï, and represented to him that they would be able, through Rabbi Moses, to sever themselves from the Gaonate of the eastern Caliphate. Abdul-Rahman, who, to his intense regret, had seen considerable sums of money yearly taken out of his land for the Gaonate, i. e., to the land which was hostile to him, was glad that a place would now be founded in his own kingdom for the study of the Talmud, and signified to the admiral the wish that he desist from his demand. Thus Cordova became the seat of an important school that was independent of the Gaonate. Moses' former fellow-prisoners also were recognized by the communities of Kahira and Kairuan as eminent scholars, and founded important Talmudical schools in Egypt and in the land of the Fatimide Caliphate. These men undesignedly severed the communities of Spain and of Mahometan Andalusia from the Gaonate. The state of politics and culture eminently fitted Spain or Mahometan (Moorish) Andalusia to become the center of united Judaism, and to take the leadership which Babylon had lost. Egypt was no longer an independent kingdom, but only a province of the Fatimide Caliphate, which had conquered it through the policy of a Jewish renegade. In addition to this, Egypt did not offer a favorable field for higher civilization, but continued to be what nature had made it, the granary of the world. The empire of the Fatimides in north Africa, whose chief town was Kairuan (afterwards Mahadia), at least afforded the principal conditions for the development of Judaism, and might well have become one of its chief centers. The rich community of Kairuan took the liveliest interest in the study of the Talmud, as well as in scientific efforts. Even before Chushiel's arrival they had had schools, and a chief who bore the title of Resh-Kalla or Rosh. Just as they had befriended and honored the banished Exilarch Ukba, they now bestowed the title Rosh on Chushiel, and enabled him to give a stronger impulse to the study of the Talmud. The latter educated two pupils during his office (950–980), and they were afterwards recognized as authorities. These were his son Chananel and a native, Jacob ben Nissim Ibn-Shahin. The physician and favorite of the first two Caliphs, Isaac Israeli, had sown the seeds of Jewish science, which was developed by a pupil of his who likewise obtained court favor.

This pupil, Abusahal Dunash ben Tamim (900–960), the head of Jewish science in the Fatimide dominions, was physician to the third Fatimide Caliph, Ishmael Almansur Ibnul' Kaim, perhaps also to his father. Dunash was held in such favor by this ruler that he dedicated to him one of his works on astronomy. Dunash ben Tamim came from Irak, perfected himself in his youth under Isaac Israeli in Kairuan, learning from him medicine, languages, and metaphysics. Dunash ben Tamim was accomplished in the whole circle of sciences then known, and wrote books on medicine, astronomy and mathematics. He also classified the sciences; in his opinion, mathematics, astronomy, and music rank lowest; next come physics and medicine; highest of all is metaphysics, the knowledge of God and the soul. The Arabs thought so highly of Dunash that they said that he had became a convert to Islam, doubtless in order that they might count him amongst their own, but he certainly remained faithful to Judaism to the end of his life. He corresponded with the Jewish statesman Chasdaï, for whom he composed an astronomical work on the Jewish calendar.

Meanwhile, though Dunash was not a genius, he was able to give the community of Kairuan, and through them to a wider circle, a more scientific understanding of Judaism. The Fatimide Caliphate, however, was not calculated to become a seat of culture for the Jews. The fanatic Fatimide dynasty—raised to power through an enthusiastic missionary, who saw in the Caliph of the house of Ali a kind of embodied divinity, and founded by a deluded deceiver who considered himself the true Imam and Mahdi (priest)—could not logically tolerate Judaism. The successors of the first Fatimide Caliph used, just as the successors of the first Christian Emperor had done, the sword as the means of spreading religion. Soon there came to the throne a Fatimide who repaired what his ancestors had in their indulgence neglected, and preached the doctrines of the divine Imamate with bloody fanaticism. In such surroundings Judaism could not flourish; it required a more favorable situation.

The European Christian countries were still less fit to become the center of Judaism than were the Mahometan kingdoms of Egypt and northern Africa. At that time the greatest barbarity prevailed there, and circumstances were not at all favorable to the development of science and literature. The literary status of the Jews was very low, and the historical reports are therefore silent on the Jewish communities of Europe. Here and there in Italy appeared Talmudical scholars, as in Oria (near Otranto), but scarcely any of them rose above mediocrity. Though the Italian Jews never attained superiority, they were diligent and faithful disciples of foreign teachers. In Babylonia they laughed at "the wise men" of Rome or Italy. Even Sabbataï Donnolo, the head of Jewish science in Italy at the time of Saadiah, could scarcely be described as a moderate scholar. This man is known rather through his career than through his works. Sabbataï Donnolo (913–970) of Oria was taken prisoner when the Mahometans of the Fatimide kingdom pressed forward across the straits of Sicily, invaded Apulia and Calabria, plundered the town of Oria, and either murdered the inhabitants or took them away as captives (9th of Tammuz—4th July, 925). Donnolo was twelve years old at this time. Ten of the chief citizens were put to death, and Donnolo's parents and relations were transported to Palermo and Africa. He himself was ransomed in Trani. Orphaned and without friends, the young Donnolo was thrown upon his own resources. He studied medicine and astrology, in both of which he made himself proficient. He now became physician to the Byzantine viceroy (Basilicus) Eupraxios, who ruled Calabria in the name of the emperor. He became rich through his medical practice, and spent his money in buying up works on astrology and in traveling. In his journeys Donnolo went as far as Bagdad. He embodied the result of his researches in a work published in 946. But little wisdom was contained in this book, if we are to judge by the fragments that still remain to us. The author, however, put so high a value upon it, that he thought that through it the name Sabbataï Donnolo of Oria would be handed down to posterity.

Meanwhile, unimportant though Donnolo was compared with his contemporaries Saadiah and others, he appears to have been far superior to the head of the Catholics at this time. This was his countryman, Nilus the Younger, whom the Church has canonized. The relations of the two Italians—the Jewish physician and the abbot of Rossana and Grotto Ferrata—serve as a standard by which we can estimate the condition of Judaism and Christianity in Italy in the middle of the tenth century.

Donnolo had known Nilus from his youth; perhaps they had suffered together when southern Italy was plundered. The Jewish physician once noticed that the Christian ascetic was very ill, owing to excessive mortification. He generously offered him a remedy. The holy Nilus, however, declined his offer, remarking that he would not take the medicine of a Jew, lest it be said that a Jew had cured him—the holy one, the worker of miracles—for that would lead the simple-minded Christians to place more confidence in the Jews.

Judaism ever strove towards the light, whilst monastic Christianity remained in the darkness. Thus in the tenth century there was only one country that offered suitable soil for the development of Judaism, where it could blossom and flourish—it was Mahometan Spain, which comprised the greater part of the peninsula of the Pyrenees.