NEW YORK (AP) – On what would have been Martin Luther King Jr.’s 77th birthday, hundreds of people including civil rights leaders, celebrities and his son gathered at a historic church to celebrate his legacy.

The Sunday service with rousing singing and speeches calling for a refocusing on King’s activism was held at the Riverside Church, where he once gave a speech opposing the Vietnam War.

Cissy Houston, the soul singer and mother of Whitney Houston, moved some in the crowd to tears with “Precious Lord, Take my Hand,” one of King’s favorite hymns.

Former U.N. ambassador and civil rights leader Andrew Young, who worked with King and helped organize the event, said King once told him that he yearned for a simpler life.

“Martin’s real dream was to be a preacher at this church,” Young told the crowd.

The event, called “Realizing the Dream,” focused on poverty. Speakers included Young, Martin Luther King III, Susan Sarandon and Jeffrey Wright, who played King in a 2001 HBO film, “Boycott.”

“My hope is that we don’t just get caught up in the celebration of remembrance but that we return to the work that he began,” King’s son said.

King III said his mother, Coretta Scott King, who suffered a stroke in August, could not attend the event.

Sarandon, who gave a reading, said she was “thrilled” to be asked to attend.

“I think this is about a reinvestment in the concepts that Martin Luther King put forward, because the battlefield has not changed,” she said.

On April 4, 1967, Martin Luther King Jr., after deliberating whether to address the Vietnam War, gave a speech at Riverside Church titled “Beyond Vietnam: A Time to Break the Silence.”

“I come to this magnificent house of worship tonight because my conscience leaves me no other choice,” he said. “Now, it should be incandescently clear that no one who has any concern for the integrity and life of America today can ignore the present war. If America’s soul becomes totally poisoned, part of the autopsy must read Vietnam.”

Parts of the speech and others by King were played during Sunday’s service, which ended as many events organized by King did, with the congregation singing “We Shall Overcome.”

Martin Luther King Jr. was born Jan. 15, 1929. Monday is Martin Luther King Jr. Day, a national holiday.