According to the Jewish sources, one of Bulan's descendants, the Khagan Obadiah, was a particularly zealous adherent of Judaism. He invited—possibly from Babylonia—many Jewish sages to his country, to instruct the converted Khazars in Bible and Talmud, and he founded synagogues, and established Divine services.
In the ninth and tenth centuries, the kingdom of the Khazars, governed by rulers professing the Jewish faith, attained to outward power and inner prosperity. The accounts of the Arabic writers of that period throw an interesting light on the inner life of the Khazars, which was marked by religious tolerance. The king of the Khazars and the governing classes professed the Jewish religion. Among the lower classes the three monotheistic religions were all represented, and in addition a considerable number of pagans still survived. In spite of the fact that royalty and nobility professed Judaism, the principle of religious equality was never violated. The khagan had under him seven (according to another version, nine) judges: two for the followers of the Jewish religion, two each for the Christians and Mohammedans, and one for the pagans—the Slavs, the Russians, and other races. Only occasionally did the Khazar king show signs of intolerance, particularly when rumors concerning Jewish persecutions in other countries came to his ears. Thus, on one occasion, about 921, on being informed that the Mohammedans had destroyed a synagogue somewhere in the land of Babunj, the Khagan gave orders to destroy the tower (minaret) of a certain mosque and to kill the muezzins (the heralds who call to prayer), explaining his attitude in these words: "I should have destroyed the mosque itself, had I not feared that not a single synagogue would be left standing in the lands of the Mohammedans."
In the kingdom of the Khazars, favorably situated as it was between the Caliphate of Bagdad and the Byzantine Empire, the Jews evidently played an important economic rôle. During the ninth and tenth centuries the territory of the Khazars was traversed by one of the great trade routes which connected the three parts of the Old World. According to the testimony of Ibn Khordadbeh, an Arabic geographer of the ninth century, Jewish merchants, who were able to speak the principal Asiatic and European languages, "traveled from West to East and from East to West, on sea and by land." The land route led from Persia and the Caucasus "through the country of the Slavs, near the capital of the Khazars" (the mouth of the Volga), by crossing the Sea of Jorjan (the Caspian Sea). Another Arabic writer, named Ibn Fakih,8 who wrote shortly after 900, testifies that on the route of the "Slav merchants," who were trading between the Sea of the Khazars (the Caspian Sea) and that of Rum (the Byzantine or Black Sea), was found the Jewish city of Samkers, on the Taman Peninsula, near the Crimea.9
During this period of prosperity the kingdom of the Khazars received a considerable Jewish influx from Byzantium, where the Jews were persecuted by Emperor Basil the Macedonian (867–886), being forcibly converted to Christianity, while hundreds of Jewish communities were devastated. The Jewish emigrants from Byzantium were naturally attracted towards a land in which Judaism was the religion of the Government and the Court, though equal toleration was accorded to all other religions. The well-known Arabic writer Masudi refers to this Jewish immigration in the following passage:
The population of the Khazar capital consists of Moslems, Christians, Jews, and pagans. The king, his court, and all members of the Khazar tribe profess the Jewish religion, which has been the dominant faith of the country since the time of the Caliph Harun ar-Rashid. Many Jews who settled among the Khazars came from all the cities of the Moslems and the lands of Rum (Byzantium), the reason being that the king of Rum persecuted the Jews of his empire in order to force them to adopt Christianity. … In this way a large number of Jews left the land of Rum in order to depart to the Khazars.
This testimony dates from the year 954. Contemporaneous with it is the extremely interesting correspondence between Joseph, the Khagan of the Khazars, and Hasdai Ibn Shaprut, the Jewish statesman of the Cordova Caliphate in Spain. Being a high official at the court of Abderrahman III., Hasdai maintained diplomatic relations with the emperors of Byzantium and other rulers of Asia and Europe, and in this way came to learn of the Khazar kingdom, through the Persian and Byzantine ambassadors. The news of the existence of a land somewhere beyond the seas where a Jew sat on the throne, and Judaism was the religion of the state, filled Hasdai with joy. Firmly convinced that he had found the clue to the lost Jewish kingdom of which popular Jewish tradition had so much to tell, the Jewish statesman at the Moslem court felt the burning need of getting in touch with the rulers of Khazaria, and, in case the rumors should prove correct, of transferring his abode thither and devoting his powers of statesmanship to his fellow-Jews. Prolonged inquiries elicited the information that the land of the Khazars lay fifteen days by sea from Constantinople, that it stood in commercial relations with Byzantium, that the name of its present ruler was Joseph, and that the safest means of communicating with him was by way of Hungary, Bulgaria, and Russia. After several vain attempts to get in touch with the ruler of the Khazars Hasdai finally succeeded in having an elaborate Hebrew epistle delivered into the hands of King Joseph (about 955).
In his epistle Hasdai first gives an account of himself and his position at the court of Cordova, and then proceeds to beg the King of the Khazars to inform him in detail of the rise and present status of "the Jewish kingdom," being anxious to find out "whether there is anywhere a soil and a kingdom where scattered Israel is not subject and subordinate to others."
Were I to know—Hasdai continues—that this is true, I should renounce my place of honor, abandon my lofty rank, forsake my family, and wander over mountains and hills, by sea and on land, until I reached the dwelling-place of my lord and sovereign, there to behold his greatness and splendor, the seats of his subjects, the position of his servants, and the tranquillity of the remnant of Israel. … Having been cast down from our former glory, and now living in exile, we are powerless to answer those who constantly say unto us: "Every nation hath its own kingdom, while you have no trace [of a kingdom] on earth." But when we received the news about our lord and sovereign, about the power of his kingdom and the multitude of his hosts, we were filled with astonishment. We lifted our heads, our spirit revived, and our hands were strengthened, the kingdom of my lord serving us as an answer. Would that this rumor might increase in strength [i.e. be verified], for thereby will our greatness be enhanced!
After long and painful waiting Hasdai received the King's reply. In it the ruler of the Khazars gives an account of the heterogeneous composition of his people and the various religions professed by it. He describes how King Bulan and his princes embraced the Jewish faith after testing the various rival creeds, and how zealously it was upheld by the Kings Obadiah, Hezekiah, Manasseh, Hanukkah, Isaac, Zebulun, Moses (or Manasseh II.), Nissi, Aaron, Menahem, Benjamin, Aaron (II.), the last being the father of the writer, King Joseph. The King continues:
I reside [i.e. my residence is situated] at the mouth of the river Ityl [Volga]; at the end of the river is found the Sea of Jorjan [the Caspian Sea]. The beginning of the river is towards the east, at a distance of a four months' journey. Along the banks of the river there are many nations living in towns and villages, in open as well as fortified places. These are their names: Burtas, Bulgar, Suvar, Arisu, Tzarmis, Venentit, Sever, Slaviun.10