Yehuda Ashlag (1885–1954) or Yehuda Leib Ha-Levi Ashlag (), also known as the Baal Ha-Sulam (, "Author of The Ladder") in reference to his magnum opus, was an Orthodox rabbi, kabbalist, social justice universalist born in Łuków, Congress Poland, Russian Empire, to a family of scholars connected to the Hasidic courts of Porisov and Belz. Rabbi Ashlag lived in the Holy Land from 1922 until his death in 1954 (except for two years in England). In addition to his Sulam commentary on the Zohar, his other primary work, Talmud Eser Sefirot is regarded as the central textbook for students of Kabbalah. Ashlag systematically interpreted the wisdom and promoted its wide dissemination. In line with his directives, many contemporary adherents of Ashlag's teachings strive to spread Kabbalah to the masses. In this undertaking, he developed a comprehensive explanation of the sequence of the creation of all of the upper worlds (Olamot Elyonim), starting with the source of emanation (Ma'atzil) and finishing with our world (Olam HaZeh). The work is divided into six volumes, containing sixteen parts and over two thousand pages. Some today consider it as the core of the entire teaching of Kabbalah.
In the 1930s Ashlag, now in his fifties, gathered around him a group of disciples, including Rav Yehuda Tzvi Brandwein, his closest student, and studied Kabbalah every night, often from shortly after midnight until dawn. He also authored many articles and letters at this time that openly promoted the study of Kabbalah on a mass scale.
thumb|130px|right|[[Ohel (grave)|Ohel of Yehuda Ashlag on Har HaMenuchot]]
Ashlag differs fundamentally from all Kabbalists of the past, who studied and taught Kabbalah in a concealed manner, in that he felt a great need to reveal and clarify the teaching of Kabbalah to the masses.
Writing of the Sulam
In 1943, Ashlag moved to Tel Aviv, and there began working on his book, HaSulam (The Ladder), a collection of commentaries on The Zohar. During this period, he wrote for eighteen hours a day, and due to a lack of money he was not able to afford a sufficient amount of paper and ink to write more precise explanations. He later said that if it had been within his capabilities, he would have written a full commentary on The Zohar in two-hundred volumes, but he was unable to begin the work only because of a lack of means.
He completed this work in 1953, and later added three more volumes. Rav Ashlag's closest student Rav Yehuda Tzvi Brandwein later finished the work by adding this three volumes called Tikkunei HaZohar "Maalot Hasulam". In honor of the completion of the entire work, his students organized a big feast in Meron, where Ashlag gave the speech that is today printed under the title “Maamar LeSiyum HaZohar” (“An Article for the Completion of the Zohar,” also known as “Speech in Celebration for the Conclusion of the Zohar”).
"Equivalence of form" with this source means having the same attributes or qualities as it, and Ashlag defines the qualities of this source as being altruistic, namely the desire to give, or in Ashlag's words, the "will to bestow" (Ratzon LeHashpia).
Through intensive study of Kabbalah, a person's desire to give to others is developed in relation to this goal. Ashlag believed that the coming of the Messiah meant that humans would attain this quality which would allow them to give up their selfishness and devote themselves to loving each other for the sake of life's purpose, as stated in the commandment "love thy neighbor as thyself." David Ben-Gurion, the first prime minister of Israel, said that "while I wanted to talk to him about Kabbalah, he wanted to talk to me about socialism and communism" and that "I was amazed that he adhered especially to Communism. He asked me several times if we will establish a communist regime after the foundation of the Jewish state." He proposed "a kind of world religion, based on altruistic social justice, in which every culture would retain its own specific religious traditions while cooperating in uprooting exploitation and poverty" and believed in "developing a community based on love between its members and a society founded on economic justice."