Av Beit Din


The av beit din, also spelled av beis din or abh beth din and abbreviated ABD, was the second-highest-ranking member of the Sanhedrin during the Second Temple period, and served as an assistant to the Nasi. The Av Beit Din was known as the "Master of the Court;" he was considered the most learned and important of these seventy members.
Menahem the Essene served as Av Beth Din in the 1st century BCE, before abdicating to "serve the King" in 20 BCE. Caiaphas was set to be next Av Beth Din but was opposed by the House of Shammai until Gamaliel became Nasi. Apparently the post of Av Beit Din was eventually filled, since the Babylonian Talmud states that Joshua ben Hananiah was Av Beit Din and Nathan the Babylonian was Av Beit Din. The Jerusalem Talmud tells the story of how Gamaliel II was deposed and Eleazar ben Azariah replaced him as Nasi. After Gamaliel was reinstated, Eleazar ben Azariah was made Av Beit Din. The parallel story in the Babylonian Talmud has Eleazar ben Azariah remaining as a co-Nasi with Gamaliel.

Modern usage

In modern times the title av beis din is often used as an honorific for the presiding rabbi of a beth din, who is typically the salaried rabbi of the local Jewish community and usually a posek. It is also abbreviated as AB"D when it is after the name of the Chief Rabbi of a national Jewish community.
It can also refer to the most senior member of the court.