As the co-founder and dean of Ohr Somayach Institutions, a Jerusalem-based yeshiva for newly-observant Jewish men, he was considered one of the fathers of the modern-day baal teshuva movement.

[5] At age 12 he left home to learn in Yeshiva Torah Vodaas,[4] where he studied under Rabbis Yaakov Kamenetsky and Gedalia Schorr.

[12] Shema Yisrael subsequently changed its name to Ohr Somayach (after the commentary on the Mishneh Torah written by Rabbi Meir Simcha of Dvinsk), in response to critics who contended that the name Shema Yisrael belonged to the entire Jewish people rather than a single institution.

[6] Weinbach oversaw the growth of Ohr Somayach into different branches, beginning with the 1984 establishment of its Israeli division.

[4] Weinbach also oversaw the development of several successful kiruv initiatives, including the Jewish Learning Exchange (JLE), a summer learning course for young men from overseas; the Ohr Lagolah teacher-training program; and the Mentors Mission, which brings American Jews to Israeli for kiruv activities.

[6] He also spoke at women's events such as the annual Shmiras Halashon Rally, and at the Mercaz Bais Yaakov high school and seminary in Geula, which he co-founded with Rabbi Yeshaya Lieberman.

[9] In his last years, Weinbach taught a daily Daf Yomi shiur in Kiryat Mattersdorf.

[4] Weinbach was diagnosed with cancer in 2007 but continued to teach, lecture and write as he underwent medical treatment.