Musnad Ahmad 30:1987

Abu Nu'aym narrated to us, Hisham narrated to us, from Qatadah, from Zurarah ibn Awfa, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him, who said: "Indeed, Allah has pardoned for my nation that which their souls whisper to them, as long as they do not speak of it or act upon it."