[8] In September 1949, Posner and his wife Risya came to Nashville, Tennessee, as the first Chabad emissaries to the state, a position they held for 53 years.

[7][10] In September 1957, Posner assumed deanship of the Yeshiva Achei Tmimim of Pittsburgh, Pennsylvania,[8] founded by his parents.

[11] Despite his out-of-state duties, he continued to guide the Jewish community of Nashville as Rabbi and Principal of the Akiva Day School for many years.

Posner's main written work is his book on Judaism in modern life titled Think Jewish and published by Kesher Press in 1979 and republished in 2002.

Posner deemed such studies as lacking in that they presented a portrait of religious communities which appeared as highly focused on traditional observance of Jewish ritual.