In 1870 Mann was invited to give an evening lecture at Temple B'rith Kodesh, Rochester's oldest and largest synagogue. This interfaith event, the first of its type in Rochester, contributed to a formal split between reformers and traditionalists within B'rith Kodesh and, according to "The Jewish Community in Rochester" by Stuart Rosenberg, "shook the Jewish community in America and even had reverberations abroad." First Unitarian and B'rith Kodesh held a joint Thanksgiving service in 1871, and Rabbi Landsberg and Rev. Mann began the practice of exchanging pulpits, with each delivering the sermon for the other's congregation. A history of B'rith Kodesh describes the relationship between the two congregations during this period as "extremely close". In 1874 First Unitarian, B'rith Kodesh, and the First Universalist Church of Rochester began their continuing tradition of holding annual Union Thanksgiving services. In 1883 Mann helped Landsberg with part of his project to translate a new prayer book from Hebrew to English. Their translation of the song "Yigdal" has been included in the "Union Hymnal" of Reform Judaism and in hymnals of other denominations, including the "Presbyterian Hymnal" (1990). In 1884 Landsberg occupied the pulpit at First Unitarian for seven weeks while Mann was ill, attracting visitors from other denominations and, according to an early Rochester history, leading to speculation about the development of a universal church. The congregation of B'rith Kodesh used First Unitarian as a temporary home in 1909 after their building was destroyed by fire.