NEW YORK -- David Letterman was back at "Late Show" on Monday after a two-week vacation, his first day at work since a threat against his life was posted on a jihadist website.
CBS has declined to comment on any special security measures being taken at Letterman's midtown Manhattan theater for the taping.
Last week, a frequent contributor to a jihadist website posted a threat to Letterman. He urged Muslim followers to "cut the tongue" of the late-night host because of a joke and gesture the comic had made about al-Qaida leaders on his CBS show. The website is a popular Internet destination for radical Muslims.
One joke among several about al-Qaida that may have helped inspire the threat was part of Letterman's monologue on his June 8 show. This was just days after the death of al-Qaida leader Ilyas Kashmiri, who was killed by a U.S. drone strike in Pakistan. Though Kashmiri was rumored to be a long-shot choice to succeed Osama bin Laden, he wouldn't have worked out even had he lived, Letterman cracked, pointing to Kashmiri's "rocky start": "He botched up the story of Paul Revere."
The real butt of that joke: Sarah Palin, potential 2012 GOP presidential candidate, who in early June on her "One Nation" bus tour claimed that Paul Revere's famous ride was intended to warn British soldiers as well as his fellow colonists.
The contributor, who identified himself as Umar al-Basrawi, wrote that Letterman had referred to both bin Laden and Kashmiri and said that in talking about Kashmiri's death, Letterman had "put his hand on his neck and demonstrated the way of slaughter."
"Is there not among you a Sayyid Nosair al-Mairi ... to cut the tongue of this lowly Jew and shut it forever?" Al-Basrawi wrote, referring to El Sayyid Nosair, who was convicted of the 1990 killing of Jewish Defense League founder Meir Kahane. Letterman is not Jewish.
Al-Basrawi, which is likely to be an alias, has made some 1,200 postings to the Muslim website, according to Adam Raisman, an analyst for the Site Monitoring Service. The private firm, part of the Site Intelligence Group, provides information to government and commercial clients on what jihadists are saying on the Internet and traditional media. Raisman said the online forum is often used by al-Qaida.
The FBI said last week that it was looking into the threat.
It was unknown whether Letterman planned to address the threat on the air.