His eldest brother, Baruch, is an entrepreneur and activist for e-bike safety[3] who has utilized free bicycle loans to bring together different segments of the Jewish community in Brooklyn.

[4] Herzfeld received his smicha (ordination) from the Rabbi Isaac Elchanan Theological Seminary in 1999, and a master's degree in Jewish history from Bernard Revel Graduate School of Yeshiva University.

He received a master's degree in medieval Jewish history from Yeshiva University under the guidance of Haym Soloveitchik; his thesis was on the topic of "Hechlid Be-Miut Simanim"[definition needed] (see Babylonian Talmud Hullin 30a).

From 2008 to 2010, Herzfeld hosted a weekly radio show called Shmoozin' with Shmuel, which was aimed at Jews in the Washington, DC community,[5] and frequently wrote columns in newspapers.

On May 23, 2014, Herzfeld delivered the opening prayer for the United States House of Representatives as a guest Chaplain.

He has been vocal on many issues, including Israel activism, Jewish outreach, the threat of anti-Semitism, gay rights,[14] and the plight of the agunah.

[17] This article generated a significant amount of media attention and put a spotlight on the agunah crisis within Orthodox Judaism.

In early January, 2015, after the deadly terrorist attacks at a kosher supermarket in Paris, Herzfeld published an op-ed in the Washington Post[18] arguing that the U.S. should do whatever it can to welcome European Jews to the United States.

Herzfeld continues to speak out in support of European Jewry, and marched with the French Ambassador at a rally in early 2015.

[24] In late 2018, Herzfeld began writing a complete Torah by hand, an enormous task which is generally undertaken by professional scribes and not by congregational Rabbis.