Musnad Ahmad 30:3108

Waki’ narrated to us, he said: Hisham and Mis’ar narrated to us, from Qatadah, from Zurarah ibn Awfa, from Abu Hurairah—Hisham said: The Messenger of Allah (peace and blessings of Allah be upon him) said; and Mis’ar attributed it to him (as a statement of the Prophet)—he said: "Indeed, Allah, the Almighty and Majestic, has pardoned for my nation that which their souls whisper to them, as long as they do not act upon it or speak of it."