As approximately 600 congregants and New York Jewish leaders packed the Altneu synagogue’s new home on Manhattan’s Upper East Side on Sunday evening, President Donald Trump’s newly appointed Middle East envoy, Steve Witkoff, cautioned that the ongoing cease-fire and hostage-release agreement between Israel and Hamas is “fragile,” with risks of a “flare-up” if not implemented correctly. 

“We have to get them [the hostages] all out. We have to implement the agreement in the correct way,” said Witkoff, who is slated to travel to Israel on Wednesday after visiting Auschwitz to commemorate the 80th anniversary of the death camp’s liberation. “The implementation here is the critical thing. The execution of the agreement was important, the first step, but without the implementation correct, we’re not going to get it right, we’re going to have a flare-up.” 

The deal will “hopefully get to phase two,” Witkoff continued, emphasizing the importance of releasing the bodies of deceased hostages after all of the living hostages are returned to Israel. 

Witkoff, a real estate investor and longtime friend of Trump who is reported to have played a key part in securing the cease-fire and hostage-release deal, shared that the death of his son, Andrew, has helped him empathize with hostage parents. Andrew Witkoff died in 2011 from an opioid overdose at the age of 22.   

Israeli President Isaac Herzog, who travelled to New York to speak at the United Nations’ service for International Holocaust Remembrance Day on Monday, also spoke at the event on Sunday — which was a dedication of Altneu’s new building. 

Referring to the Jewish belief that saving one life is equivalent to saving the world, Herzog commended Witkoff for helping to secure the release of seven hostages over the last two weeks. 

“I can attest to the fact that you have already saved seven souls out of Gaza,” Herzog said. “And six more hopefully will come out this week.” 

“I want to wish you well on your special mission on behalf of President Trump, which is an opportunity to thank the president for his incredible commitment,” Herzog said as the crowd, which spilled into overflow rooms, erupted in applause. “And I want to wish you the best of luck in your endeavor of trying to bring peace to our region.”  

Also in attendance was Sen. John Fetterman (D-PA), who in brief remarks told attendees that when he heads back to Washington, his “voice and vote is going to follow Israel.”  

Others spotted in Altneu pews included Michael Herzog, the former Israeli ambassador to the U.S.; Danny Danon, Israel’s ambassador to the United Nations; Ofir Akunis, consul general of Israel in New York; Eric Goldstein, CEO of UJA-Federation of New York; Malcolm Hoenlein, former executive vice chairman of the Conference of Presidents of Major American Jewish Organizations; Rubin Schron; George Klein; and several Jewish members of New York City Mayor Eric Adams’ administration including Moshe Davis, senior liaison of community affairs; Menashe Shapiro, deputy chief of staff and senior advisor to the mayor and Richie Taylor, deputy NYPD chief.