Musnad Ahmad 1034:91

Abu Qatan narrated to us, Shu'bah narrated to us, from al-Hakam, from Ibrahim, from Hammam ibn al-Harith, who said: A man passed by, and they said: "This is one of the informants of the princes." Hudhayfah said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "The talebearer (qattat) shall not enter Paradise."