He served as chairman of organizations such as the Central Conference of American Rabbis and World Union for Progressive Judaism.

Jacob wrote a book, Christianity Through Jewish Eyes in 1974, leading to interfaith dialogue.

He founded the Solomon B. Freehof Institute for Progressive Halakhah in 1991, an international forum for Jewish law.

In Germany, he co-founded the Abraham Geiger College, the first rabbinic seminary in Central Europe since the Holocaust, in 1999.

Helped by American relatives, the family managed to flee Germany in 1939, first to London, and a year later to the United States.

[1] He served as vice president of the World Union for Progressive Judaism,[1][2] and chairman of its International Responsa Committee from 1990 to 1994,[1] and was president of the Central Conference of American Rabbis from 1992 to 1994,[1][2] emphasizing a broader Reform interpretation of the Jewish law (halakhah).

[1] Jacob took a leading role in interfaith dialogue with his book Christianity Through Jewish Eyes, first published in 1974 and revised in 2007,[1] which led to close friendship with Catholic bishops.

[1] Jacob was awarded the Order of St. Gregory the Great from Pope John Paul II in 2005.

[4] Jacob founded the Solomon B. Freehof Institute for Progressive Halakhah in 1991, an international forum for Jewish law that he served as its first chairperson.

[2] He co-founded the Abraham Geiger College, the first rabbinic seminary in Central Europe since the Holocaust, as part of the University of Potsdam in 1998,[1][4][8] serving as its president.