Abdullah I of Jordan
Wallach was the personal physician of many Torah leaders of the Old Yishuv, among them Rabbi Chaim Hezekiah Medini (the "Sdei Chemed"), whom he treated in Hebron, Rabbi Yosef Chaim Sonnenfeld, Rav of Jerusalem, Rabbi Yosef Tzvi Dushinsky, the first Dushinsky Rebbe, and Rabbi Solomon Eliezer Alfandari, who lived in the Ruchama neighborhood (today Mekor Baruch). He also treated King Abdullah I of Jordan.