Samuel G. Freedman / New York Times News Service

MAHWAH, N.J. — In the months after his father’s murder in early 1999, those months stretching formlessly between the mourning ritual of shiva and the impending trial of a suspect, Rabbi Joel Mosbacher received many messages of solace. There was one type, however, that tested every atom of clerical forbearance he possessed.

“People said in this trying-to-be-helpful way, ‘This will make you a better rabbi,’” Mosbacher, 43, recalled. “And nothing made me angrier. I didn’t want to be a better rabbi. I wanted my dad back.”

He wanted Lester Mosbacher, who had been shot dead in a petty robbery at his small business on Chicago’s South Side the day before he turned 53. He wanted the father who cheered the White Sox and gardened in the backyard and barbecued with a flashlight or umbrella if necessary. He wanted the grandfather for his firstborn son, just 11 months old at the time of the murder.

As Joel Mosbacher raised his own family and advanced in his rabbinical career, moving from an assistant’s position outside Atlanta to a senior one in this New Jersey suburb, he recognized that no prayer, no fast, no act of religious charity could give him what he wanted.

Yet on a Sunday afternoon this month, Mosbacher stood before an assembly of 200 clergy members, congregants, politicians and police officials in a North Jersey church to tell, in the cause of gun control, the story of his father’s murder.

“All he did was drive to work, as he had done for 35 years, and he was stolen from his brothers, wife, his children and grandchildren,” Mosbacher said. “I’ve carried this story with me, this anger, every day for the last 14 years.” Then he made reference to a verse from Leviticus: “I won’t stand idly by my father’s blood.”

What Mosbacher was proposing was not just support for the gun control legislation then pending in the Senate. In fact, rather presciently, he warned the audience not to “hope for the best from the most dysfunctional institution in America.”

Specifically, as a leader of the faith-based coalition New Jersey Together, he was propounding its proposal that local mayors, gun retailers, firearms manufacturers and large buyers like the military sign a “covenant” of gun overhaul measures.

Mosbacher had delivered a similar speech for a similar purpose in February in Chicago before 500 members of United Power, a sister organization of New Jersey Together, under the rubric of the national Industrial Areas Foundation. He had delivered it to a similar group in Westchester County. He had delivered it from his own pulpit at Beth Haverim Shir Shalom in Mahwah on Super Bowl Sunday.

While the rabbi had done a bit of tentative speaking on gun control as early as 2000, his commitment accelerated after 2006, when he first learned about the Industrial Areas Foundation. As a legacy of the renowned community organizer Saul Alinsky, the foundation largely mobilizes religious congregations. Its style, far from being earnest, is proudly combative.

One of the foundation’s major principles is that anger, if channeled correctly, is welcome, for it derives from the Norse word angr, which can mean sorrow or grief at the condition of the world.

“It went past my brain right to my heart,” Mosbacher said of the exegesis of angr. “It felt like the closest thing to me to a revelation.”

The lesson on angr also evoked the prophetic tradition within Judaism. Mosbacher heard in angr echoes of Micah’s admonition to “to do justly, and to love mercy,” as well as Deuteronomy’s command that “Justice, justice shalt thou follow.”

Then, in the past year, the rabbi’s prophetic summons arrived in grisly form: 12 people shot dead at a Colorado movie theater last July, six worshipers shot dead at a Sikh temple in Wisconsin the next month, 20 schoolchildren and six educators shot dead in Newtown, Conn., in December.

“The piling of murder upon murder and funeral upon funeral made me wonder if this is the moment when the people of this country, people of faith, would wake up,” Mosbacher said. “And I felt that I brought with me more than suburban guilt to the work of doing justice in this country. I brought a story, even if I didn’t tell it at first.”