Just a few months after his retirement, Jon Stewart made a visit to “The Daily Show” on Monday to talk about a health care act for 9/11 emergency responders that he had helped champion when he hosted the program.

Mr. Stewart, who stepped down in August from “The Daily Show,” the Comedy Central news satire he had hosted for more than 15 years, popped up in the second act of the program, now hosted by Trevor Noah. “I’m sorry, sir,” Mr. Noah joked. “Are you — are you lost?”

Mr. Stewart, dressed casually and sporting a silver beard, said that he was not there to take back the show, but to talk about an issue that he cared about “very deeply, and I want to get some attention paid to it.”

That issue, Mr. Stewart said, was the James Zadroga 9/11 Health and Compensation Act, which provides health care funding and compensation for emergency workers who were sickened by the terrorist attacks of Sept. 11 and their aftermath. The act passed Congress in 2010, was signed into law by President Obama and went into effect the following year. Portions of the act expired after Sept. 30, and the rest of it will expire by next October unless it is renewed.