The Author was secretary of the Jewish community of Cologne. Aaron is known for his participation in the important controversy known as the Cleves get. Having personal knowledge of the entire case from its inception, Aaron sought to reverse the decision of Tevele Hess of Mannheim and of the Frankfort rabbinate who had declared the divorce invalid. In conjunction with Israel b. Eliezer Lipschuetz, he appealed to all rabbis of authority in Germany, Holland, and Poland to permit the divorced woman, Leah Gunzhausen, to remarry. The majority expressed agreement with his point of view. He collected expert opinions and published them under the title Or ha-Yashar (Amsterdam, 1769; reprinted Lemberg, 1902, with notes by Jekuthiel Zalman Schor entitled Nizozei Or.).