For forty-two years (1880–1923), Hirsch served as the rabbi of Chicago Sinai Congregation, one of the oldest synagogues in the Midwest.

From Chicago Sinai's pulpit, he delivered rousing sermons on the social ills of the day and many Chicagoans, Jews and Gentiles alike, were in attendance.

He also wrote studies of the historical relationship between Judaism and Christianity, including appreciations of its founding figures Jesus and Paul.

[1] In addition, he published a number of articles for the Reform Advocate, a weekly journal which he edited for thirty years.

In keeping with his interest in education, Hirsch advised a wealthy congregant, Julius Rosenwald of Sears, Roebuck & Co., to use part of his wealth to help build public schools for black students in the segregated South; their facilities were consistently underfunded.