Rabbi Ephraim Eliezer HaKohen Yalles (also written in Yiddish as Yales) (born 5th of Shevat 5651, 1890 – passed away 25th of Cheshvan 5749, 1988) was the Chief Rabbi of Sambor and later the Chief Rabbi of the Orthodox community in Philadelphia.
After the arrival of the Previous Lubavitcher Rebbe (Rabbi Yosef Yitzchak Schneersohn) to the United States, Rabbi Yalles approached him with a request to study Kabbalah and Chassidus together. The Previous Rebbe referred him to his son-in-law, Rabbi Menachem Mendel Schneerson (the Lubavitcher Rebbe). After the passing of the Previous Rebbe in 1950, Rabbi Yalles was among those who strongly encouraged the Rebbe to accept the mantle of leadership in Chabad.
From that point onward, Rabbi Yalles became a regular participant in the Rebbe’s farbrengens (Chassidic gatherings) and established a deep personal connection with him. Rabbi Yalles regarded the Rebbe as his personal spiritual guide and would visit him several times each year.
Their relationship was particularly close, as evidenced by the Igrot Kodesh, a series of volumes containing the Rebbe’s letters, which includes hundreds of Torah-related letters exchanged between the Rebbe and Rabbi Yalles, addressing topics in both the revealed aspects of Torah (Nigleh) and Kabbalah.
Rabbi Yalles demonstrated deep attachment and devotion to the Rebbe, to the point where he would refer certain complex Torah and science-related questions to the Rebbe. One famous example involved a question on astronomy, concerning a perceived discrepancy between the size of the sun as described in Jewish sources and as measured by modern science. Rabbi Yalles deferred the question to the Rebbe, displaying his strong trust in the Rebbe’s guidance and wisdom.
Rabbi Yalles' relationship with the Rebbe was characterized by great respect and a sense of bittul (self-nullification) toward the Rebbe. He relied heavily on the Rebbe’s teachings and leadership, both in matters of Torah study and personal guidance, and maintained a strong connection to the Rebbe throughout his life.
This bond reflects Rabbi Yalles' reverence for the Rebbe, not only as a halachic authority but also as a spiritual guide who embodied both the revealed and hidden dimensions of Torah.