In the Schechter Letter

Schechter Letter

The "Schechter Letter" was discovered in the Cairo Geniza by Solomon Schechter.-The Letter:The Schechter Letter is a communique from an unnamed Khazar author to an unidentified Jewish dignitary...

, Serakh is the wife of the Khazar ruler Sabriel

Bulan (Khazar)

Bulan was a Khazar king who led the conversion of the Khazars to Judaism. His name means "elk" in Old Turkic. The date of his reign is unknown, as the date of the conversion is hotly disputed, though it is certain that Bulan reigned some time between the mid-700s and the mid-800s. Nor is it settled...

. A Jew, she encourages her husband and other Khazars to convert

Religious conversion

Religious conversion is the adoption of a new religion that differs from the convert's previous religion. Changing from one denomination to another within the same religion is usually described as reaffiliation rather than conversion.People convert to a different religion for various reasons,...

 to Judaism

Judaism

Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...

 and establish it as the official religion of Khazaria.
Serakh is not mentioned in the Khazar Correspondence

Khazar Correspondence

The Khazar Correspondence was an exchange of letters in the 950s or 960s between Hasdai ibn Shaprut, foreign secretary to the Caliph of Cordoba, and Joseph, Khagan of the Khazars. It is one of the few documents known to have been authored by a Khazar, and one of the very few primary sources on...

 or the Kuzari

Kuzari

The Kitab al Khazari, commonly called the Kuzari, is one of most famous works of the medieval Spanish Jewish philosopher and poet Rabbi Yehuda Halevi, completed around 1140. Its title is an Arabic phrase meaning Book of the Khazars...

.

Some scholars have postulated that the Khazar conversion to Judaism came as a result of contact with existing Jewish populations in the Crimea

Crimea

Crimea , or the Autonomous Republic of Crimea , is a sub-national unit, an autonomous republic, of Ukraine. It is located on the northern coast of the Black Sea, occupying a peninsula of the same name...

 and the Caucasus

Caucasus

The Caucasus, also Caucas or Caucasia , is a geopolitical region at the border of Europe and Asia, and situated between the Black and the Caspian sea...

, possibly the ancestors of the Krymchaks

Krymchaks

The Krymchaks are a Turkic people, community of Turkic languages and adherents of Rabbinic Judaism living in Crimea. They have historically lived in close proximity to the Crimean Karaites...

 or Mountain Jews

Mountain Jews

Highland Jews, Mountain Jews or Kavkazi Jews also known as Juvuro or Juhuro, are Jews of the eastern Caucasus, mainly of Azerbaijan and Dagestan. They are also known as Caucasus Jews, Caucasian Jews, or less commonly East Caucasian Jews, because the majority of these Jews settled the eastern part...

. As with so much of Khazar studies, the absence of documentary evidence renders the question of whether Serakh belonged to one of these groups a matter of speculation.