Mordechai Tzemach Eliyahu, was an Israeli rabbi, posek, and spiritual leader.
Mordechai Eliyahu
Blessing and autograph of Mordechai Eliyahu circa 1998
In Jewish law, a posek is a legal scholar who determines the application of halakha, the Jewish religious laws derived from the written and Oral Torah in cases of Jewish law where previous authorities are inconclusive, or in those situations where no clear halakhic precedent exists.
Toledot HaPoskim, History of the Jewish Codes, by Chaim Tchernowitz.